Final answer:
The Spanish initially reacted with outrage, but ultimately ceded Florida to the US in the Adams-Onís Treaty.
Step-by-step explanation:
The Spanish reaction to John Quincy Adams demanding their territory in East Florida was multifaceted. Initially, they were outraged by the violation of their territorial integrity and demanded that Adams and his troops withdraw. However, realizing that conflict with the United States would continue, Spain ultimately opted to cede the Spanish colony to the US in the Adams-Onís Treaty of 1819. This treaty officially transferred control of Florida to the United States in exchange for $5 million, and also set the boundary between the United States and Mexico.