What were the various challenges the Spanish Empire had to face?

The major challenge that the Spanish Empire had to face
was the challenge from other European nations.  Other European countries wanted to gain
their own empires and to eat away at Spanish domination.  As they attempted to do these
things, they presented major challenges to the Spanish
Empire.

Two major challenges to the Spanish came from the
English and the Dutch.  The English were competing with the Spanish for empire in the
New World.  In addition, English pirates and privateers were preying on the ships that
carried the wealth of Spain's empire back to the mother country.  The major Dutch
challenge to the Spanish Empire came from their attempts to break free from that
empire.  The Dutch wars of independence took a major toll on the Spanish in terms of
money and effort.

These sorts of challenges from European
countries inside and outside of the empire were a major threat to the power of the
Spanish Empire.