I don’t know if I’d go so far as to say the U.S. is ungovernable. It’s just that a weapon has not yet been developed to make it stick.
Power at the national level creates extreme inequality between the few who hold office and the rest of us who do not. Basically, we can vote in elections, and that is it. With power more localized, we have a greater chance of holding office or having influence as voters. More important, we could “vote with our feet” by moving to jurisdictions that suit our preferences.
People already do this, but for the most part they stay in the U.S. That could be changing if a growth in centralized power results in more of a Generica.