We all know that the American colonies depended on slave labour to a considerable extent. Indeed, Portuguese were taking slaves from the Gold and Guinea coast and selling them from mid 1400s, first in Europe and later in the Americas. Suppose another industrial/trade power decided to interrupt it because it could not afford its native sugar/spice/textile industry ruined by cheap production using slave labour (while it was dependent on hired labour, which was more expensive), what would be the effect? In particular, if one industrial power (in my case, a navally powerful Vijayanagar) decided to ruin the slave trade by arming the natives/destroying the slaver ships, etc in the mid sixteenth century, what would be the effect in Europe and America?
How would it be seen in Portugal and in the remainder of Europe? Ideas would be greatly appreciated