There was no USA in 1619. Some how simultaneously you want the nation to be responsible for a small percentage of slave owners within it, but also be responsible before the nation even existed? Shit why don't we throw in the slaves that built the pyramids while we are at it.
Oh sorry... my bad, I should have read a history book.
So, anything before 1776 isn't part of the USA's history?
One day, English people living in North America, decided that drinking tea was for too posh and instantly transformed into American, dismissing all their previous actions (slavery for example) to the fact that they used to be "English", but now they are "Americans" so total reset on everything, and we start a new count on slavery.