My great grandfather was born in Ireland. Wexford to be exact. This comes back on my Mum's DNA. Including to the point that it picks up Wexford. Indeed she comes back as 50% Irish. She was born in England as was her mother. My Mum technically may qualify for an Irish passport I believe.
However she also comes back with bits of Dutch DNA and Danish DNA Does this mean she's Irish or Dutch as opposed to English? Indeed when we talk about Danish DNA this can actually refer to someone who can trace their ancestry back many many generations in England to a particular area of the country - we are talking hundreds and hundreds of years. And this is distinctly different to other places within England. It doesn't actually say they are remotely Danish - they just share a particular DNA marker that's distinctive.
It's nonsense to suggest she Irish or Danish or Dutch.
She is of Irish ancestry. This doesn't mean she's culturally Irish. It doesn't mean she's ethnically Irish either because she a mix or ethnicities.
But we don't talk about this because we can't see it. She's white.
Equally there will be lots of people who don't have white skin who are of various ancestry - and many will have a mix from a number of regions which we'd lump together into a singular nationality which doesn't understand the ancestry of people from that area of the world. We have this notion based on rather ignorant ideas of ethnicity and culture.
If we go back to my original comparison with Americans who had an ancestors on the Mayflower and can claim some English Ancestry - this doesn't mean they are remotely English. They are distinguishable as having ancestry from a particular place - but they are also identifiable as distinctly different in DNA from someone English - their DNA profile might identify which part of England they had ancestors from but it would also pick up that they settled in a particular part of the US and are uniquely different to people who still live in England.
Likewise it isn't going to be long before distinctive DNA profiles appear in people born in England who are of Caribbean or Pakistani ancestry for example. They won't look like a DNA profile from someone from Pakistan - even if they have remained within within a British Pakistani community genetically. They will be unique to England/Britain. (Yes your head should be starting to hurt at this point)
This is typical and has been going on for as long as we can distinguish in DNA - the genetic isopoint is about a thousand years. For England this happens to fall at the same point as the Norman invasion. This will slowly shift later and later with each new generation. In a thousand years someone who is a 2nd generation now (so born in the UK) will appear as 'English'. If we had done DNA tests on people in England in 1066 we'd see some very different things to what we see now. And yet, we recognise the descendants of the Normans as 'English' and we the descendants of the Vikings as 'English' and profiles of those who could trace their ancestors a thousand years back in England would look very distinctively different.
The idea that we are somehow genetically or culturally threatened in a way that is a crisis is one for fuckwits who don't have the first fucking clue about changing migration patterns, ever changing DNA and ever changing mixing of people's from around the world.