I've lived in other countries. There is racism and xenophobia in every country that I've lived in. Not just the UK. It's the same mentality everywhere.
It seems to be driven by a misguided notion of : humans think they own a patch of land. We own this land. Its ours. And foreigners are not welcome here
Then they put visas and hoops that foreigners have to jump through to say that they can stay on the land.
Yet even when these people are granted citizenship, they are looked down on as " new land".
So if a person's parents move to the UK, and they have a child born in the UK, that child will be looked down on as "not really from the UK".
It's like new money. I was in Ireland last week and I have an Irish friend there who is married to a Nigerian woman. They have a daughter. The daughter puts up online videos about life in Ireland and being irish. They told me she gets comments all the time that she is not really irish. Even though she was born in Ireland to an Irish father. Like people make such a stupid big deal about nationality
People want you to have lived in a place for ten generations before they see you as being from that place.
When in reality no one owns a patch of land. People move around all the time.
if you look back far enough, a lot of our ancestors moved to the UK from other countries too