Well certainly the slave and cotton trade was a dominating part of the early American economy.

>The average slave owner held almost two-thirds of his wealth in slaves in 1860, much less than he held in land.

https://www.encyclopedia.com/history/news-wires-white-papers...

"America was built on slavery" is obviously a bit of hyperbole, but given the economic boost to agriculture in the south built on the backs of African slaves, or the literal building of the east-west infrastructure on the backs of Chinese ones, I don't think it's an unfair claim.