So I guess you should define "European". If you mean anyone with at least 50% European blood than many if not most Latinos would qualify. If you mean 99% or higher European blood than you have to somehow prevent mixed marriages...
Ok... I'm going to make something arbitrary that excludes most of them just to make this easier... Do note this isn't a scientific definition of European, but just something I'm making up so that people don't get into arguments if population X qualifies or not.
Let's go with people with "low melanin skin content," ">7/8 European ancestry"
and "could be confused for a native Englishman, an Irishman, a Welshman, a German, a Scandinavians, an Italian, a Spaniard, an Italian, a Hungarian, or Romanian." Mind you, they don't have to be of
that ancestry, and I think lots of say... Russians can fit that description. But very few Latinos qualify (I mean, some could pass of as a native Spanish thanks to actual European ancestry, but most wouldn't).
Under this circumstance, a 75% or greater European population never happened in OTL since 1900 all the way to the present. Would making the English use more indenture servants instead of buying slaves from African Warlords be a POD enough to change that, assuming similar environmental events in OTL (an Irish potato famine does indeed happen, your imagination on if this changes NA demographics like OTL or not... I really don't know)? Or maybe not slave trading would simply lead to more use of latino labor?