England imposed the institution of slavery on the American colonies by means of their regulation of economic affairs. It didn't occur spontaneously from market dynamics, but was specifically provided for by (their) laws.
It wasn't just some government flex.
You also haven't addressed any of the other negatives that unregulated market dynamics have manifested.
The "American colonies" were, of course, not limited to the modern USofA; Sir John Hawkins of Plymouth aka "the Pioneer of the English Slave Trade". formed a slave-trading syndicate in 1554.
He sailed with three ships for the Caribbean via Sierra Leone, hijacked a Portuguese slave ship and sold the 300 slaves from it in Santo Domingo. During a second voyage in 1564, his crew captured 400 Africans and sold them at Rio de la Hacha in present-day Colombia, making a 60% profit for his financiers.
Caribbean colonies were of course quite different.