It's clear that you truly believe in what you wrote, and I respect that. However....
There is one very large thing that most Europeans don't quite understand about America, through no fault of their own. In Europe, each country is able to interact freely with the countries around them so well mainly because most European countries are very similar in terms of culture and lifestyle. It's easy to live in harmony with people whose culture is nearly identical to your own. How many differences are there really between someone from Finland and someone from Sweden for example? Not many, so of course the countries get along well.
America is the complete opposite. We have quite literally every culture in existence living in the same cities in some places (like New York City). When you take people from 100+ different cultures, who all believe in entirely different things, then force them to live right next to each other for years upon years.... it does not promote global unity. It does the opposite and creates hatred, jealousy, cultural clashes, gang wars, etc.
People simply can only take so much of being forced to live with and accept other cultures who have completely opposite lifestyles before they snap. It becomes even worse when the countries leaders attempt to force everyone to "just get along" and absolutely destroy anyone who dares to think for themselves instead of just accepting whatever the leaders want them to accept.
Genuine American culture has been damaged so badly by forced changes, and being forced to treat certain cultures like they can do no wrong. Europeans don't understand that in America if a non-Middle Eastern person accuses a Middle Easterner of doing anything wrong, immediately they become a target and are barraged from all sides with accusations of things like racism, xenophobia, hatred, prejudice etc. What are people supposed to do? Only say good things about the person who just robbed your store and shot your brother because they happen to be Middle Eastern? Apparently that's what some of the politicians want.
Even the laws of the country themselves have been changed to give certain cultures preference over other all other cultures, for absolutely no reason other than that a politician felt like making it that way. The affirmative action law is a perfect example of this. Let's say there are two people applying for a job as manager of a restaurant. One is a white man with a bachelors degree in business management. The other is a black man who has a highschool diploma but no college degree. Both people are exactly the same in every way other than education. The affirmative action law says that BY LAW the restaurant is forced to hire the black man simply because he is black, even though the white man was a more ideal candidate for the position due to the college degree. Tell me, how is that fair in any way? Just because someone happens to be a minority they somehow deserve the job more than someone who is better suited for it? Things like that have been going in on America for the last couple of decades. People of Middle Eastern, Latino, and African descent have gotten extreme preferential treatment from the government and whenever anyone protests against such clearly unfair laws and regulations they are accused of being a racist, prejudiced, white supremacist Nazi. The media demonizes anyone who doesn't want to comply with their "white people should feel guilty for being white" philosophy. The politicians pass increasingly unfair laws that give certain minority cultures massive advantages over all other cultures for no reason at all.
They have even gone as far as allowing teachers to press their political beliefs on little kids that are like 8 years old, to brainwash them to follow a certain political philosophy by the time they are of voting age. I am a teacher, I have seen this first hand many times. If a child mentions ANYTHING that supports the Republican party during a class discussion about politics or whatever else, many teachers will shut the kid down instantly and tell them that what they said is wrong, racist, and has no place in school even though what the student said was not racist in any way, and was a fair discussion topic. I have seen teenagers literally suspended from school by their teacher for daring to bring up an alternative viewpoint during a classroom discussion, in a respectful way. In one particular case that happened recently the student was suspended for saying that they do not think women should be allowed to have direct combat military jobs because it could endanger the lives of male soldiers with the same job if the female soldier wasn't physically able to do their job during a fight due to the genetic differences in strength between the genders. That sounds like a completely fair point that could have created a good class discussion right? Apparently not, the student was suspended for "sexism" and then later expelled entirely after he and the parents fought back against the school for doing it.
When our own politicians who are elected to serve the country, absolutely refuse to follow the basic laws of the country, like deporting illegal immigrants, it causes normal Americans who believe that people should follow the law to become very unhappy and resentful of their government. This is one thing that I can't wrap my head around at all, in every single country in the entire world, it is against the law to break into the country without going through the proper procedures and having the proper documentation. The people who do it anyway are even literally called "illegal" immigrants. Yet the leaders of this country adamantly refuse to remove the people who broke into the country illegally, and in a lot of cases refuse to even call them illegal immigrants because apparently doing that is "racist". They call them "undocumented" immigrants instead. Breaking into a country is illegal. Doing something illegal makes the person doing it a criminal. Therefore all illegal immigrants who broke the law to get in are criminals by default. Yet whenever anyone publicly calls an illegal immigrant a criminal, they are accused of being a racist. It makes no sense to me.
The religious differences cause problems as well. I am an Atheist so don't believe in any religions at all, however I completely understand why so many Christians are angry that their religion is being stomped on by the government in favor of Middle Eastern religions. Your original post was about global unity and everyone being friends. How can an American Christian be friends with their Muslim immigrant neighbor, when their neighbor believes all non-Muslims should be executed because it says so in the Quran? I'm not saying all Muslims believe that of course, because that isn't true, but the most dedicated followers of Islam actually do believe that. How can you possibly trust and be friends with someone who chooses to follow a religious philosophy that tells them their purpose in life is to execute people like you? If a radical Islamist runs through the street screaming "Death to America!" it's completely ok, and they will not be punished for it at all. If a Christian or Jewish person runs through the street screaming "Death to Islam!" they will be arrested by the police and thrown in jail for hate speech. How is that fair? It's a double standard created by the politicians in this country to further their political agenda.
As I said at the beginning of this post, Europeans cannot truly understand what it's like to live with these things every day because Europe is so different from America culturally. Since Europeans don't deal with things like this on a daily basis it's very easy for a European to say that global unity and multiculturalism would be a great idea when they have never actually experienced it like Americans have. For the first time ever certain parts of Europe like Britain have begun to experience the problems that I mentioned in this post due to things like the Syrian refugee issue, and as we all saw Britain fought back against it in the form of the Brexit vote. They realize that British culture is slowly being destroyed just like American culture was destroyed, and they are trying to fix it before it's too late.
Things like what I mentioned in this post are why a candidate like Donald Trump is so popular, and why people are tired of the government telling them what to think, what to say, and how to say it.
I am an independent and don't belong to a political party. I don't particularly like Donald Trump, however after seeing the current politicians do their best to destroy what's left of American culture I will probably end up voting for him.
In your original post you mentioned that America is great because of it's spirit, and things like America's involvement in World War II. I agree with you, but the World War II American culture doesn't exist anymore. That was genuine American culture, and it has been ripped to shreds by our current politicians. I just hope it isn't too late to bring it back.