I don't understand very well the question because your same reasons, Atlantic Economy, wich, when? in front of, columbian exchange? What's this? Thinking about i can only propose:
1. Atlantic Economy: the Triangular Trade.
Manufactured goods of Europe, slaves from frica and plantation products of Amrica like caribean sugar or northamerican tobacco. So i believe that your professor is thinking in the commerce (and consequently, the culture) Thirteen Colonies - USA in modern age, specially XVIII century (1700-1800)
2. Columbian Exchange: ???? and ???? Try: Columbian from Columbus i believe, your professor is thinking about the initial motivations of the europeans when they discovered Amrica, trade with the East, Gold, to make native slaves and serfs.
Hypothesis: The deep purpose of your professor is, if i'm in the right way, that you think and write about the crucial factor in the development of USA, and the answer is clear, the anglosaxon way of development wich they showed many time after Columbus is far more important, USA isn't related to the 1492 ambitions but to the work of the angloamericans in trade, industry and agriculture of 1700 wich were far more profitable and the pilars of the nation.
But dude, wasn't you going to classrom??