Have heard this since I was a child, however the site says Ephraim is USA while Mannaseh is Great Britain. I always heard it was flipped and America is Mannaseh and Great Britain is Ephraim. (Mannaseh was prophesied to be a "great nation", while Ephraim was prophesied to be a "multitude of nations", which bears out as Great Britain is indeed comprised of many different nations; Canada, Australia, etc... while America is one singular nation).

Other western nations supposedly are the other Hebrew tribes. Altogether the entirety of the western nations are the descendants of the original Hebrew tribes. Or so I've heard from various sources over the years.