One of the factors that allowed native americans in mexico to settle cities larger than those in areas to the north was that central american contained more gold that acted as currency and made the economy jump
The Union blockaded the South, making it so trading ships couldn't come or go.
Hunters and gatherers were mainly scavengers and lived off of what they could find and agricultural communities could grow their own food and also sell it for a profit with no worries. Hope this is right! :)