A direct election for the President, with ranked-choice voting, and a system of FPTP for Congress (definitely not pure democracy, which I happen to value like yourself), is nothing like a pure democracy when put together. It would last. All that you might need to do is bundle a few states together — because seriously the differences between Wyoming, the Dakotas, and Montana, for example, are not particularly deep-seated. Reduce the number of states to about 30 so none feel without influence, and then you’ve got an institution which is both democratically legitimate and sustainable. It’s fine to have a system of slightly limited democracy, but the extent of the US’ problem with democracy is huge.