I haven’t seen anyone mention Mississippi John Hurt or Rev. Gary Davis yet. Most of the fingerpicking guitar style that found its way into folk, rock and country is a direct result of those two teaching their playing style to the Folk Revival crowd in the 60s.

It's mostly a matter of preference. While the word 'country' is often used interchangeably with 'sovereign state', it's not like the word is reserved only for that use. In the UK, country is just the word that they use for the major administrative divisions, similar to states, provinces, prefectures, and the like.

It is true that that preference reflects the historical status of those regions as independent kingdoms, but that is not something that is unique to the UK (Hawaii, Bavaria, Sicily, Saxony, etc)