Final answer:
The attack on the USS Maine became the final push towards war between the U.S. and Spain.
Step-by-step explanation:
The incident that became the final push towards war between the U.S. and Spain was the attack on the USS Maine. In December 1897, riots in Havana threatened U.S. lives and property, so President McKinley dispatched the battleship USS Maine to protect them. In February 1898, an explosion on the ship was blamed on a Spanish mine, and with newspapers and the public calling for revenge, Congress declared war on Spain in April 1898.