Which Event fieled American jingoism and inflamed relations with Spain

The correct answer is:

The publication of a letter written by the Spanish ambassador that insulted the president.

A personal letter written by Spanish Ambassador Enrique Dupuy de Lôme, in which he insults President William Mckinley and refers to him as "weak, and stupid politician", was published in American newspapers. This letter is called "The de Lôme letter".