I think you're ideologically motivated, and arguing from a position of emotional distaste for trans people rather than unbiased concern about medical practice. Here's why:
> any legitimate discussion or criticism about gender-affirming care, possible social cause that's driving the increase of trans-identifying teenagers
Trans-identified is a term created by anti-trans activists initially as an "in joke" because calling someone a trans identified male or trans identified female created acronyms that spelled traditionally female and male names: TIM and TIF, where TIM would be applied to trans women and TIF would be applied to trans men. A group that is serious about improving the world wouldn't choose their terminology so as to make fun of or harass people. A hate group would.
> or how certain trans rights infringes on women's rights
It's not at all clear that trans rights infringe on women's rights. The right to segregate yourself from elements of the population that you find distasteful isn't guaranteed. Otherwise we'd still have Jim Crow laws in the American South and lesbians would still be barred from women's sports due to concerns about them being predatory in locker rooms - yes this was a big concern in the 1980's.
> the capture of cultural institutions by radical activists
This is conspiratorial thinking. "Institutions" are made up of individuals and operate under some guiding principles. They aren't captured like territories in a game of risk.
> This would also mean that statements made by countries that are arguably more progressive than the US (i.e. UK and European countries) about the current trans issue would fall into that category as well.
The UK and EU have different politics than the US. They are economically more egalitarian, but socially can be very conservative.
> it's hard to believe that the medical and activist organisations in the US are actually acting in good faith
Why would you conflate medical and activist organizations? Isn't it possible that you are the activist, and that you'd like to bend medical organizations to your will because they disagree with your own prejudices?
> Anyone of sound mind can clearly evaluate that my point isn't transphobic. The reply to this comment is a demonstration of what's wrong with the US.
Saying that nobody can disagree with you unless they are mentally unwell, and then calling someone who disagreed with you an example of "what's wrong with the US" is very odd behavior. It doesn't seem like the way someone operating in good faith would behave.