There is a big difference between legal immigration and illegal. Open borders have been tried before, didn’t work out so well for the American Indians or Mexico when the opened up TX to all US immigration.
We actually do remember our past, some of us do anyway.
Correct, those whose family came on the Mayflower look at many as johnny come late-leys who ruined the country. And some of then especially detest the catholics from Ireland and southern Europe. Then there are these descendents of Spanish/Mexican who arrived in what is now the US long before all or many white europeans
The notion of legal versus illegal is a relatively new construct.