The last time a US politican slammed the Brits like this may have been Seward during the Civil War - but of course it was a calculation for him (wrong as it happens, but...)
If R$y is calculating here I suspect he's dog whistling to his gang back home, knowing he can pivot again if he is elected.
Then again he just may be as socially clueless and morally lacking as he seems..
The Brits have been responding with some snipes against him and his religion - as long as they fixate on him rather than the country...
Or ... From Anonymous ;)
Maybe he's banking on his red-neck base known the English only as the bad guys from their primary-school history of the American revolution and "Braveheart."
Maybe he feels that he has to swagger and demonstrate US supremacy at every turn - that's best done by pointing out the inferiority of aliens at every point.
"of course he may also be completely clueless "