Why couldn't Spain hold on to its colonies in America?

There are several reasons why Spain was unable to hold onto most of its colonies in America in the early nineteenth century.
One key reason for Spain's loss of colonies was its occupation under Napoleon. Napoleon's troops occupied the country for many years, and the nation was the scene of the Peninsular War (1808-1814). Although French troops were finally ejected, the country was badly weakened.
A second reason for Spain's difficulties was the powerful example set by the United States in the late eighteenth century. The US had fought and won a war of independence from Britain. This inspired people in Latin America to do the same.
The final reason for Spain's loss of its colonies was its defeat at the hands of rebel forces. After years of battles throughout the vast regions that comprised Spain's colonies, the rebels remained unconquered. By 1820, there was a rebellion in Spain itself, and the American colonies—except for Cuba—achieved independence.