Final answer:
The statement is true, as Andrew Jackson's military actions in Florida led to negotiations that culminated in the Adams-Onís Treaty of 1819, in which Spain ceded Florida to the United States.
Step-by-step explanation:
The statement in the question regarding Andrew Jackson's military excursions into Spanish-held Florida, the failure of the Spanish government to protect the territory, and the subsequent acquisition of Florida by the United States through the Adams-Onís Treaty in 1819 is true. In 1818, Jackson led forces into Florida to address conflicts with the Creek and Seminole Nations, and in the process undermined Spanish authority there. This along with other factors compelled Spain to negotiate.
The Adams-Onís Treaty occurred as a result of various pressures and actions; one of which was Jackson's aggressive campaigns. Spain ceded Florida to the U.S. for $5 million, relinquished its claim to Oregon, while the U.S. temporarily renounced claims to Texas. This treaty importantly contributed to territorial expansion of the United States