There are no political parties in the united states, on paper. Each representative is free to vote however they like, for whatever reason they like, once they are in office. Some states have a way to recall federal representatives, but not all do.

Unlike parliamentary systems you are not (on paper) voting for a party, who appoints a representative; you are voting specifically for a singular person, who may associate with a party.

Now because 250 years have happened between that idea and how congress actually works, the entirely made up and not constitutionally supported positions of ‘House majority leader’ and ‘Senate Majority leader,’ exist. These positions do not exist in the constitution, and did not exist for most of the country’s history. But these positions are now used to appoint committee assignments, and decide what legislation is voted on (primarily, there are ways to force votes, but that requires a supermajority of representatives agreeing to do that). Again these positions that effectively control how congress functions have no basis in the constitution, did not exist before 1925, and go directly against the purpose of congress and the concept of a political party-free government that the US was designed to be as to not descend into the corruption the founding fathers saw in the house of lords in the UK.

But they’re super important now, because the corruption is too entrenched to get rid of.