Europeans know what made America great. Just ask them. America is the only country in the world that is founded on an ideology, and not ethnicity. Americans are all different nationalities, races, religions, and cultures, but until fairly recently, they were united on a set of ideals: Mainly, the rights of the People trump the rights of government (there is no monarchy or formal aristocracy). And this affects virtually everything, from religion to economics to pop culture.
Unlike in most countries, if the government wants to force you to do something, or they want take your stuff, or they want to prevent you from doing something, THE GOVERNMENT has to prove its case, before force can be exerted. You are INNOCENT until the Government proves you guilty. If the government wants your land, they have to give you a hearing and PROVE that Government needs it, AND they have to give you a fair price for it. If the Government ***** you, you can sue the government, and WIN!
The Government has NO RIGHT to prevent you from saying what you want to say in this country. In Europe, there are various hate speech laws that allow people to be thrown in jail if they say something that even remotely offends someone, and THEY TAKE THOSE LAWS SERIOUSLY. Here, that only applies on College campuses.
The Government has NO RIGHT to establish a "Welfare State," even though most Western Democracies have done so. Why? Because the Constitution forbids the Government from setting up a Welfare State. It would take a Constitutional Amendment.
Originally, America was "great" because of Judeo-Christian morality, which was reflected in the laws of virtually every state. Now, not so much.
When Trump talks about making America great again, he is subliminally criticizing the previous President, who felt that he was a citizen of the world before a citizen of the United States. And ironically that might have been true.