For sure, we can cherry pick points in time relative to human migration, and establish notions of nativism...And yes, some notions of nativism are older than others.
So the US was/is broadly speaking a European colony with a shorter history, never able to establish a native identity other than "white"...And of course pre-white US nativism was irredeemably colonised and absorbed.
Ahhhh...And but then there are all manner of browns and blacks and enforced or economic migrants, who procreate just as white-man does, whose US-ness is almost as brief as Paddy the Irishman's or Herman the Germans...Or should I say Trump the German.
And over here, for a long time we were a general mixture of mostly European whiteness, perhaps tinged with Mediterranean sun...Though latterly we too exposed ourselves to the vagaries and riches of the broader planet and it's colourful people.
So Britain is as Britain does and Britain has become what it is, and the restoration of a general whiteness thereof, is a pipe dream of tattooed boneheads and older regressives...Because "white" Britishness being largely apathetic, tends not want to get greatly involved.
Hmmm,,,I would like to go on but I have places to go and things to do...So have a nice day GG.