What would happen to the little racists if Europeans did leave America? Who would pay for and keep up their free schools, free hospitals, free roads, free apartments and houses, free sewage and water sytems, free economy, etc.?
If Europeans left America, these little racist know-nothings would have the US looking like Mexico in the space of ten years. Then they would be screeching at Europe - "Give us free stuff."
It is going to take many generations before this mob of idiots is equipped to run the Nation. They should start by figuring out what the rule of law means (require literacy) and why it is an important concept in creating all the free stuff they get from the gringos they hate.
I think it would look more like China since the chi-coms would quickly move in and begin exterminating the know-nothings.