The Americans thought that the USS Maine was sunk by a Spanish mine. This incident lead to what we today know as the Spanish-American war of 1898.
At this time, there was a Spanish presence on Cuba as their government was trying to extinguish a Cuban resistance movement that wanted to liberate Cuba from Spanish rule.
Because the Americans thought their ship was sunk by the Spanish and because they were strongly in favour for Cuban independence, this lead to the aforementioned war.