Proportional representation also has its problems. Look at the Netherlands, which has 17 different parties in parliament and led to it becoming increasingly difficult to form coalitions, see:
I'm confused when you wrote "becoming increasingly difficult to form coalitions". Mark Rutte has been PM since 2010. Wiki says: "On 2 August 2022, he became the longest-serving Prime Minister in Dutch history..." Without specific examples that demonstrate a trend, the term "increasingly difficult" is editorial-speak. Also, look at NL economy for last 30 years. Looks pretty good compared to any other highly developed country. That is very difficult to do without a high functioning govt.
You might not approve of where the “center” is in the US, but Democrats absolutely represent the center left and republicans represent the center right of the actual American electorate.
Yes, but since the US is a more right-wing country than the rest of the developed world (healthcare, death penalty, taxes...), that would mean the Democrats are "centrist" and Republicans "right." Characterizing based on relativity to the developed world seems much more fitting, since we're discussing it between people mostly from other developed countries and in a thread about Britain.