Sadly you are right.Trump is a petulant child who will never accept receiving home truths - just look at his utterly insane reaction to Zelensky calling it as it is, that Trump is "trapped in a Russian disinformation bubble". Much as there would be some satisfaction to see Starmer shred Trump on live TV, all it would achieve is Trump doubling-down on his lunacy.
GB is not a big player in all this. Starmer can make the right noises, but sadly it will have zero influence on the Orange Shitler, as I saw him referred to on here earlier. He'll literally do whatever the f*ck he wants.
As for referencing the Americans who fought and died and are buried in Europe for standing against tyranny - Trump (who dodged the draft 5 times during the Vietnam war) once referred to them as "losers". He's not the full ticket.
If Starmer came armed with a video showing Trump and Putin discussing about how to steal Ukranian wealth and siphon the money into their private bank accounts, Trump would just say 'fake news' and 70 million Maga oafs, plus @spence would applaud.