The correct response is: "Spain realized that the expense and trouble of maintaining Florida outweighed its usefulness and agreed to sell it."
The First Seminole War (1816-1819) highlighted Spain's difficulties in controlling its territories and managing conflicts with Native American tribes, particularly the Seminoles. This led to increasing pressure on Spain to cede Florida to the United States, culminating in the Adams-OnĂs Treaty of 1819, where Spain formally ceded Florida to the U.S.