The problem with the U.S. system is twofold: first, an unusually high amount of cooperation is required to pass any law (majority of the House, 60% of the Senate, and the presidency). Second, the first-past-the-post electoral system naturally leads to a two-party duopoly and polarization that makes cooperation very difficult. No other democracy in the world has both of these flaws although some have one of them (e.g. the UK).

The best systems in practice seem to be proportional-representation parliamentary ones. They generally result in coalitions of multiple generally centrist parties so things don’t change too abruptly, but passing new laws is at least possible. Of course some parties refuse to cooperate with each other: in Germany for example no mainstream party will work with the right-wing AFD, and right-leaning mainstream parties additionally refuse to work with the left-wing Die Linke (legal successor to the East German ruling party although substantially more moderate nowadays). However this doesn’t stop the big mainstream parties from working together to an extent that would be unimaginable in the U.S.

It’s indeed probably impossible to fix in the U.S. because it’s so hard to amend the constitution in such a radical way.