Yes, if the UK ATC infrastructure can cope with the requirement to provide Area QNH on request 24/7.....
...which, at the moment, they certainly cannot.
I think I have to differ slightly there... There seems to be more statements/readbacks of QNH nowadays in the UK than ever, both in the air and on the ground. If in doubt, say the QNH seems to be the new rule!
As a regular visitor to US airspace, I've not found it particularly onerous, given that passing transition on the way down, you're probably within 70nm of destination; closer when operating into the higher altitude airports of the Mid-West. Most of the time you get one, maybe two QNHs - in the UK you get it going through transition and then seemingly every time you change controller...
The only time you get repeated changes of QNH in the US is if you're going a long way at low level, like routing round the back of New York to get to EWR. Even then, it's not a particular chore.
It doesn't take long to say "Altimeter 29.97" or "QNH 1015" compared with all the other guff that goes out over the airwaves...