Historically this was true around most of the world where slavery existed, on every continent in just about every culture at one point or another in history. But that's what it is now in our nation...history, not current reality.
Hmmm....I have no idea what you mean by this assertion. Perhaps you've bought into the 1619 Project propaganda and misinformation?
The American economy was not based on slavery. The American economy was as diverse as ever, with small businesses, farms, mining operations, trade, manufacturing, etc..
The bulk of slave labor with a few exceptions was used in agriculture, including cotton production. Where unskilled manual labor would be more costly if paid laborers were used. With the exception of the cotton gin which made picking cotton more profitable, advances in technology over time typically reduced the need for raw unskilled manual labor. Still, farming remains a moderate manual labor endeavor even today where machines like Harvesters and seeders are used.