Trying to explain this again.
Ancestry (and every other firm) assigns ethnicity by comparing your DNA with other, living people. In particular, they have "control" groups, which are made up of people whose established "known" ancestry is all from one country for several generations.
There is no such thing as "English DNA", or Scottish, Irish, Norwegian, Indian, Outer Mongolian or anywhere else, for that matter.
What there is, are particular strands which are very common amongst the population now living in England, Scotland, Ireland etc. One would assume that for example people living throughout the UK share a lot of common DNA, but Ancestry matches that with the part of the UK where it is most common, and in particular where it appears in the DNA of people whose families have lived in one area for a very long time.
Take my own DNA for example. Ancestry predicts that I am 87% Scottish and 13% Irish. That's it. Not a drop of English blood in me (though as a matter of fact I was born in Bristol). Perhaps more significantly, Ancestry doesn't suggest any Scandanavian ancestry either, yet the paternal side of my family are all from Ayrshire and Argyll, as far back as we can trace. Anyone who knows their Scottish history will be aware that at one stage the entire west coast of Scotland, especially the islands and places like the Cowal peninsula were settled by Norsemen, whose longships were by far the best form of transport between the settlements perched on islands and sea lochs from Sutherland right down to Dumfries and Galloway.
Those Norse settlers farmed the land, raised animals and raised their own families. Over time they married into "native" Scots families and Scots married into their families. The DNA of both groups became mixed. It seems inconceivable that my Argyll ancestors are "pureblood" Scots. There must be some Norse blood in their somewhere. I have no doubt that some of my Ancestry originates from the old Viking realms, and that I have some "Viking" DNA. But so does everyone else whose family have lived in Scotland for generations.
When Ancestry compare my DNA with the DNA samples they already have, mine most closely matches the DNA of other people whose known ancestry is Scottish. That's all.
