Thanks for picking up on the important content there. ;-)

If you want to be pedantic, Merlin - assuming he existed in the most likely timeframe - probably was aware of Angleland to his east, and would have been defending against its encroachment. (This based on the rise of Arthur as a popular name around 550AD as I recall, during the "Saxon" invasion largely carried out by Angles). The country he lived in was probably called something like Britain, though may have simply been closer to Cymru.

But I was largely paraphrasing T.H. White's Once And Future King, which in turn cribs the La Morte d'Arthur, which forms the basis for the "modern" Arthurian legend, and recasts it in an idealized England.