I think the arguments that Rockzmom and Throbert McGee gave about being a multinational country are valid and good arguments for trying to encourage a bit of nationalism. I understand that this is something that the USA has to handle, and that emphasising history and achievements is key to that. For me, the idea of a truly "multicultural" country is exciting and interesting.

What we have in Europe with the traditional population + "refugees" is just a weird and frustrating situation. In many cases the cultural clash is extreme and there is really no way for them, with their culture, level of education and religion to be a part of society.

America is different from Europe in that way. And I think that most people who emigrate to the USA are probably keen to put their past behind them and willing to identify as Americans.

My impression is that the USSR tried to get people to feel "Soviet" rather than anything else, but they probably did not succeed very well with the majority of people for different reasons.
Perhaps when Soviet people thought of the experiences of the the War, and about sports, they were able to identify with that nationality, but otherwise not...

The EU is another example of an artificially created country that is trying to create some kind of unity. However, the 'propaganda' for this is quite low key. Kids are told that the EU is a very successful peace project for Europe, which is essentially true, although there is more to the story.
Everyone can see the benefits for themselves when they travel in Europe, and compare with the past with endless wars that benefited practically nobody.

You don't really feel "European" until you LEAVE Europe and compare yourself with people on some other continent - that's when you realise how much we have in common despite language differences. The level of enthusiasm about the EU varies a lot between countries too.

My issue with American values / nationalism is that it is sometimes used as part of the motivation for invasions etc. I.e. "there is no "freedom" in this country, we need to liberate them (and their natural resources...)". The values that are relevant for Americans are not necessarily what other people want - and if they do, let them get it themselves! What the US gets up to, in my view, is just a modern take on colonialism/imperialism - but twisted around in such a way that it is hard to recognise.

But invading a country and forcing your values on them, and obtaining their resources cheaply, IS imperialism, regardless of whether you talk about democracy and freedom, or Queen and the need for christening the pagans....
That is my view, anyway.