It's not that. Adele doesn't want to alienate a large segment of her potential fan base by making it appear as though she is endorsing a U.S. presidential candidate. I'd do the same thing.
And, FWIW, Adele needs no help getting airplay.
I agree as an expatriate English lad living in Canada, with your observation. In addition to that, though not interfering in U.S. politics, I like the Donald. If the corrupt and nasty minded British press decided to destroy Adele professionally they could do this. Now they cannot lay a glove on her.
Not to be discounted is the absolutely mindless hissy fits shown by the British media. This by the spectre of a President Trump. Coming close is the urbane and holier than thou put downs of Trump in the Canadian media. Drumming up their denigration of the Donald. Completely ignoring or just not knowing about the Constitution of the United States. That Constitution does have a system of checks and balances. I must concede that there is some difference of opinion regarding the incumbent in the White House and the implementation of the Constitution