Why did Federalists believe the Louisiana Purchase would weaken their country and its central government?

The Federalists were against the Louisiana Purchase because they thought that a large nation would be nearly impossible to govern from Washington D.C. They worried that the new land would splinter off and form its own country. Even if the new land did not form its own country, there was a possibility the new land would form new states that would have Democratic-Republican leanings which would weaken the Federalist base in New England even further.
The Federalists also had more selfish reasons for this. Thomas Jefferson made the purchase without getting prior Congressional support and the Federalists did not want the Democratic-Republicans to gain popularity for enlarging the nation. There was also the fact that the land deal was done with Napoleon. The United States gave Napoleon millions of dollars for this property—money that Napoleon could use in his war against Britain. Since the Federalists were Anglophiles, this was unacceptable. The Louisiana Purchase thus proved to be quite controversial in its day.