American democracy could be significantly improved just by adding term limits Senators and Representatives, plus an age cap for Congress and the President. Taking steps to break the two party system would be even better.
I personally like Germany’s approach to parliamentary representation, where you vote for both a district representative and a party. Once the district seats are filled, more seats are added until each party is proportionally represented. This goes a long way to reducing the spoiler effect and helping third parties get a voice.
I know this is a controversial take, but I actually like the electoral college in principle. The goal of the electoral college is to balance the interests of urban and rural voters so that whoever wins the election will hopefully be good for both. Currently, electoral votes are distributed based on the results of simple majority votes at the state level, with some states including a ‘winner takes all’ rule. If it were up to me, I’d instead use state level alternative votes or something similar, and ban the 'winner takes all’s rule.
However, I don’t think we will see any of these in a very long time, if ever. The current system benefits the people currently in it, why would they change it? IIRC, the UK had a referendum to switch voting systems years ago, and their two biggest parties banded together to pressure voters to keep the existing system.