Slaves and immigration sceneries

Why are the immigration rules and regulations now what they are in US?

Just look back a few hundred years. The White people were lazy, and imported their own slaves from Africa. Now - were these Blacks, Africans, slaves, POSSIBLE legal immigrants? Or had they filed all their K-1, K-3, i-130 paperworks in the Outside-European British Embassies before the slaves were imported?

And what if the Native Americans, Indians, call them how ever you prefer, would have had the same immigration policies?