I see your fears, and there’s definitely the worrying possibility of the world spiralling into war or other unrest with the move towards populism in recent times.
But I think you’ve missed one thing:
America is currently great, according to pretty well any statistics.
Namely, this. What you don’t mention is that America (and much of Europe) is only doing well for people near the top of the economic scale. If you’ve wealthy (like say, making millions as a CEO, making hundreds of thousands in tech or just come from a slightly more well off background than usual), then yes things are great. Goods and services are cheaper than ever. Your every need can be met via the ‘sharing economy’. Etc.
But there’s also then much of the rest of the population, and this is where things aren’t so good. Increasing automation means less and less jobs for those in other fields. Globalisation means lots of jobs that would otherwise be in the US or Europe are exported abroad so companies can save money on wages and working conditions. Housing prices are getting so insane that only the rich can seemingly afford them in many areas.
And neither the government nor the left seems to care. They’ve set their sights on targeting the upper middle and upper classes. Helping multinational corporations do better seems to be more of a focus for politicians than helping regular people improve their lot.
So a lot of poorer people (both from the traditional working class and various immigrant populations) feel abandoned by the government and political system, which they feel seems to be favouring elites over them.
And this provides an opportunity for the populists and facists and extremists for all stripes. It lets them blame immigration or the EU or whatever else as the ‘cause’ of all the country’s troubles. It gives terrorist groups like IS the chance to market towards disaffected youth that feel lost in life with talk of ‘glory’.
Not to mention, a lot of ‘outsider’ politicians who market themselves as the ‘solution’ to the divide between the political class and population.
Economic and social inequality leads to terrible situations and extremists. This is what will lead to social unrest and possible war if not sorted out. It was a factor in the rise of the Nazi party, Communists in Russia and various civil wars (like in France), and I very much worry similar things could be in the future here for the same reasons.