Final answer:
Spain lost the most territories in The Americas in the first three decades of the 1800s due to the independence movements in Latin America.
Step-by-step explanation:
Spain lost the most territories in The Americas in the first three decades of the 1800s. After Latin America achieved independence from Spain in the early 1800s, Spain began losing control of its colonies in the Americas.
These new countries of Latin America went through a period of struggle to establish stable governments and economies, leading to the loss of territories for Spain.