Yes, I'm very concerned about American decline. In particular, because elections are now about ad spending rather than leadership performance, the underlying assumption of democracy may no longer apply. People today vote based on the propaganda effect - repeated slogans and narratives that break down resistance and create tribalism - rather than assessing their own interests or values. It doesn't matter how incompetent a politician proves themselves to be, as long as the money is there to buy the ads to sway the voters who stare at screens 5+ hours a day and consider their internet experience to be a valid part of reality.
The result is federal and local governments that cannot solve basic problems, such as winning wars, removing lead from drinking water, having an effective law enforcement / judicial system, managing natural disasters, or replacing crumbling bridges. Political ineffectiveness has led many Americans to cynicism. A quarter of millennials in a 2018 survey said electing leaders is unimportant, and only 19% disagreed with the statement that “military takeover is not legitimate in a democracy.”. These pro-coup sentiments suggest the U.S's democracy could collapse within our lifetimes.
https://www.nbcnews.com/think/opinion/democracy-essential-millennials-increasingly-aren-t-sure-should-concern-us-ncna847476I remain mostly invested in the U.S. though, because it is a culture where money buys not only power, but the right to survive. To be poor here involves heightened risk of death by crime, pollution, law enforcement, diet-related illness, and a lack of healthcare to a much greater extent than people face in most other developed countries. American culture is about working long hours so that you can live in a relatively safer neighborhood, send your kid to a relatively better school, hire a good lawyer if you get into legal trouble, and maintain health insurance coverage. American culture is also about propping up the stock market at all costs, and ensuring that profits make their way to shareholders. Sure, lots of people in Europe and Asia work hard too, but the systems for incentivizing labor in those countries are arguably not as brutal (unless you are a Uyghur in a Chinese forced labor camp). Also, a greater percentage of corporate profits in Asia and Europe are directed toward welfare states or ruling parties, but in the U.S. profits are directed to shareholders, who ensure it stays that way by financing the ads which swing elections.
In a nutshell, the U.S. system is uniquely designed to extract the most work and consumption possible out of its people, and return the vast majority of those profits to shareholders. The FIRE movement is an effort to cheat this system by becoming a large enough shareholder to escape most of the incentive/disincentive structure that compels people to spend their whole lives working. One simply has more FIRE leverage in U.S. stocks vs. stocks in high tax / high regulation social democracies or in dictatorships like Russia/China/Phillipines/Thailand.
If the U.S. changes to being a one-party oligopoly like Russia or China, I'll pivot to investing in democracies elsewhere in the world based on the assumption that the U.S. government / ruling party will take an increasing slice of profits from investors through corruption or nationalization. However, many of these cultures, such as South Korea, Chile, Japan, Australia, Western Europe, South Africa, India, etc. will be subject to the same pressures that fell the U.S, so the universe of investible places could shrink dramatically in the coming decades.