AS far as I know Ancestry does not have a US
Ethnicity Apart from.natve Americans
My American relatives have Scottish/ Irish Welsh /English /European Jewish ethnicity
Have you misunderstood how the DNA ethnicity works . It shows emigration of communities and locations where your matches live if you look at maps but if you look at the ethnicity of your matches compared to your own it will be accurate
No I haven't misunderstood. Ethnicity is derived from DNA segments believed to be common to individuals descended from a particular region. How accurate it may be at any particular level is open to a degree of questionability.
But besides ethnicity, you also referred to a community of Devon and Cornwall. Ancestry's communities are derived from locations in common to the more recent ancestors of you and your DNA matches, and are determined from the location information in your and their family trees, for ancestors who lived in the same places over a similar period of time, not from any information in your or their DNA, other than the genetic autosomal matching that connects you and directs Ancestry's algorithm to run its trawl through those trees.
North American communities are certainly not restricted to indigenous Americans. One of the communities that my brother and I share is Ohio, Indiana and East Kentucky Settlers (1700-1975) which Ancestry describe as "The pioneers of German and English ancestry who crossed the Appalachian Mountains in the late 18th century".
In respect of which, Ancestry also say, "You, and all the members of this community, are linked through shared ancestors. You probably have family who lived in this area for years—and maybe still do. The more specific places within this region where your family was likely from: Southern & Central Indiana, Southwestern Ohio & Northern Kentucky."
As I say, my family have never been to or settled in any of those locations, but numerous half cousins descended from my GGF did emigrate to and settle in those areas. No-one from my direct line, certainly within the last 300 years, which Ancestry Communities are supposed to represent.