Vote for lesser evil + organize, get loud and make being trans normal in red states. The American system is so screwed up with no ability to dissolve your legislatures before the 4 year cycle. If you live in a state of those races, it would be better to be ignored than your rights taken away. If you need anything go seek the support of a Democrat that is pro-trans from out of your state, with control of Congress they would be able to help you more if your state's legislators are useless but of the same caucus rather than of a caucus that is actively blocking efforts. Sorry if I sound flippant about it, but I would tell moderate voters the same about a progressive candidate.
If you're worried about the ratchet affect, the solution I don't think is to turn the screws further in the direction of the ratchet. The UK example is weird, the Labour Party's somewhat to blame but I don't fully lay it at their feet, because their justice system is biased in very old ways, negatively affecting people's rights to gender expresssion.
The USA has already tried in 2016 the "haha, let Republicans vote for Donald Trump, they'll see how bad it is when they vote for racism rather than a milquetoast candidate and they will disavow it forever after" method, that didn't work, only made things a lot worse, he got elected again. Even if you have the long game in mind, not voting appears to send, even if a Republican wins 49% to 47%, a signal that the people mandate that trans people should be hurt, rather than a more neutral signal. States that had been trending red turning blue signals nationally a change in the direction of trans acceptance, regardless of the willingness of the candidate to associate during the campaign with pro-trans advocates or not.