Comment by legitster

The US constitution has a really bad early adopter syndrome where it was so good at the time that it's hard to move away from. Nearly every country with a constitution modelled on ours has failed at some point.

"We basically run a coalition government, without the efficiency of a parliamentary system" - Paul Ryan.

To be more specific, our majority-based government locks us into a two-party system where one party just has to be slightly less bad than the other to win a majority. But our two parties are really just a rough assembly of smaller coalitions that are usually at odds with each other.

The presidential democracies that function usually have some sort of "hybrid" model where the legislature has some sort of oversight on the executive office. But they are still much more prone to deadlock or power struggles.