Which is based on the Supremacy Clause, federal law preempts state law, even when the laws conflict. Thus, a federal court may require a state to stop certain behavior it believes interferes with, or is in conflict with, federal law.
1<span>The federal government was not given the power to regulate trade.
</span>2 <span>The federal government needed approval of the states to collect taxes.
</span>4 <span>The state and national currencies competed with each other.</span>
I think the answer is the Columbian Exchange.
I hope this helps :)