The decline of the Spanish Empire was a complex process caused by a multitude of factors like;
Overextension: Spain spread its resources too thin across a vast empire, making it vulnerable to internal and external pressures.
Economic mismanagement: Dependence on American wealth and neglect of domestic industries led to financial instability.
Military setbacks: Losses like the Spanish Armada and the Dutch Revolt weakened Spain's global power.
Internal strife: Political and religious conflicts weakened the central government and hampered effective administration.