I never really thought about until you mentioned it, but the American and English species really don’t intermarry or even interfriend.
They’re not much over here and we’re not much over there.
I know we fight well together, but do our soldiers party with their soldiers?
Well during WW2, it was not so much with with the British 'Tommies' as with their girlfriends and others. The well known Brit complaint during the Normandy build-up was that the Yanks were "Over-paid, Over-sexed and Over HERE!" Given that most of the British Troops were spread over many fronts after 4+ years of fighting, there was reason for that animus. The Yanks were also somewhat successful in their endeavors in Britain given the number of war brides they came back with!
Trust me, I have done some serious interfriending with the Brits. And I’m half-Irish.