There many possible coalitions, but there is actually just one with which you end up with, and into which you do not contribute.
Of course you (and other voters) contribute. The biggest party typically is one that forms the coalition and the vote share and recent performance at the poll among other things affects that.
I am not talking about compromises inside the party. I am talking about compromises that you are forced to make when you select one or another party.
They are the same sort of compromises. There’s a reason every round people are unsatisfied with the result, even if their party won.
Are you arguing that US parties are too similar?
No?? I’m saying the parties do similar sort of politics as they’ve been doing for decades. Voters swinging to the left has little effect when it’s the same Democrat party in rule. Or same for right wing. You need something dramatic for the position to actually move.