The first major domestic crisis of the US government under the Constitution resulted from the federal government exercising its new right to tax the states in order to bring in more revenue to pay down the war debt.
Federalists believed that the central government should be strong and have a lot of power. They held a loose interpretation of the Constitution, meaning they believed that, if the Constitution didn't say you couldn't do something, you could do it.
Napoleon sold Louisiana to the United States because at that time in the early 1800s, France was in a bitter war with surrounding European nations and suffered large amounts of debt from Napoleon's tyrannous rule. He didn't have enough troops to secure France during these wars while at the same time shipping more troops to America to govern Louisiana. Also with Spanish territories to the American west and the U.S. to the east it was difficult for Napoleon to enter into Louisiana due to America taking over the Mississippi River. As a result, he had no choice but to annex the Louisiana Territory to Thomas Jefferson for a cheap amount of 15 million dollars ~ roughly 10 ¢ per acre.
