"There are two parties in the US. These parties are centrist, big-tent, and from a policy standpoint, don’t dramatically differ."
If you think this, then I can see why you disagree. I'd have to ask by what measure do you make this claim? Or compared to what exactly? Personally I think this opinion out of date.
In my view, depending on how you look at it, the US has either 2 or 3 parties. Democrats, Republicans and MAGA. Traditional Republicans are so diminished some, myself included, consider them to not even be relevant. Heck Dems are more like traditional Republicans than Republicans are now.
MAGA is not centrist or big-tent and there are enough of them that can break things or hold hostages or say elect a religious lunny to be speaker of the house. They cling to extremist positions and absurd conspiracy theories, and attempt to force their will on to others. They run impeachment proceeding based on zero evidence with the hope they will turn something up to have to talk about and since there is nothing to find apparently, they literally make stuff up. They do not want to fund Ukraine for, some reason, and presently they are winning on that.
Jaysyn