I believe it was Spain. they were the ones who discovered a lot during that time period.
The French first introduced slavery to the Mississippi territory in the early 1700's
Trade barriers restrict or reduce international trade which reduces international cooperation among states and the overall interdependence. For example, if you rely on another country to buy cocoa and they rely on you to get sugar, if you enact trade barriers, you won't get cocoa and they won't get sugar which will be a huge problem for both industries in both countries because you depend on each other.
