The seeds of the United States began not in 1619 with the introduction of slaves but in 1492 when a European, Columbus, discovered 'The New World'
By 1619 many settlements had been established before any African slaves arrived.
1619 is not THE story. It's only one aspect of the story.
Jamestown was founded in 1607. There is much to be learned from what happened there in the 12 years before any Africans were present in what was then the only English colony in mainland North America.
What should be remembered most about 1619 is the creation of the House of Burgesses--the beginning of the tradition of self-government in the English colonies which later became the US.