Final answer:
The USA acquired Florida through the Adams-Onís Treaty of 1819 after strategic military actions and diplomatic negotiations, involving a payment of $5 million to Spain.
Step-by-step explanation:
How the United States Acquired Florida
The acquisition of Florida by the United States was largely due to diplomatic efforts following military actions. It was achieved through the Adams-Onís Treaty of 1819. During the War of 1812, the U.S. seized control of West Florida. After the war, General Andrew Jackson invaded Spanish-controlled East Florida to address conflicts with Indians, which provided Secretary of State John Quincy Adams leverage in negotiations with Spain. Concerned about its waning control over its New World Empire and the ongoing revolutions in Latin America, Spain was under pressure. Consequently, Spain ceded Florida to the U.S. for $5 million and relinquished its claim to Oregon, while the U.S. temporarily renounced claims to Texas. This treaty was instrumental in facilitating American continental expansion.