My first Canadian ancestor was Leonard-Tremi (Jonas) Le Roy baptised 1674 in what is now Quebec.
My first Ontario born ancestor was Levi Peer who was born 1807 in what was then Upper Canada.
My first born American ancestor was Styntje Jans Snediker born 1641 in New Amsterdam (now New York City)
Caveat: I've omitted my Mohawk ancestor Ots-Toch (wife of Cornelis Van Slyke) because I have no idea of her ancestry going back in time but it certainly was hundreds of years before Styntje.
My husband has no American ancestry. His first born Canadian ancestor was Ellen Montgomery born in 1822 in Quebec. Johannes Alexander Allen Butler, son of his black ancestor, was a close second being born in 1824 in York County Ontario.
Who was your first North American ancestor?