You don’t need to anticipate societal shifts, you need to empower the political system to handle them.
As for the longevity of the U.S., there’s a strong argument that it has in fact not lasted 250 or so years, and that the reconstruction era amendments created a qualitatively different, more centralized country. But even if we ignore that, the U.S. has a lot going for it that has nothing to do with politics. Two oceans, peaceful neighbors, and more natural resources than we knew what to do with that we bought for practically nothing.
The US emerged from WW2 as basically the only advanced economy that wasn’t flattened, did essentially zero introspection and assumed our politics were superior. And yet we have open bribery of politicians, and the highest court opened the floodgates for the wealthiest to donate to politicians. The only thing left is to allow politicians to keep donations for personal use.
Europe has surpassed us in life expectancy, and soon China will surpass us in GDP. And no matter how much free speech we have, we can’t have a conversation about it because the media is weaponized to distract us.