The greatest difference between the US and the UK is just that: the US is a far more chaotic, violent, and generally unpleasant society compared to the UK, but it has an extraordinarily robust legal system and institutions that balance each other's power so that nobody is ever really in full control. The UK is a fairly pleasant place to live--at the moment. But things are starting to go downhill a bit, the government is becoming, ever so slowly, more authoritarian, and there is no legal backstop: in the end, the UK is an absolute monarchy with an embodied sovereign power, everything goes back to the Crown. If a far-right party comes to power and parliament becomes effectively dissolved, there is no telling how far and how rapidly they could change society.
That is simply not the case in the US, where, in fact, a right wing populist did come to power, did try to subvert the election process, did try to (indirectly) eliminate congress, and failed on every front. And he failed so hard that people might re-elect him since they don't think he could succeed the second time around anyway. Yes, people shoot each other all the time, the violent crime rate per capita is incredibly high, and society in general is plagued by inequality and racial tension. But the chaos drives the country forward. The UK is quiet, calm, comfortable (workers schedule their strikes!) There is no room for real organized dissent. It would take the dissolution of the monarchy for real change to come about, but they aren't going to do that here. They aren't going to do anything.