How did the explosion of the U.S.S. Maine stir war fever?

It created tension between the U.S. and Spain

Remember, the Maine had American lives onboard.

The Maine blew up, and the U.S needed a good reason why. They blamed the explosion on the Spanish (even though, years later we found out the Spanish didn't do it at all). The U.S. made campaigns saying "REMEMBER THE MAINE, TO HELL WITH SPAIN!"

That's how the USS Maine was involved. This is not the only thing that stirred war fever. A Spanish Diplomat also wrote a letter criticizing the U.S. president. In other words, he said things that American citizens didn't want to hear.

Also, the U.S wanted more land. And by going to war with Spain, the U.S took Spain, the Philippines, and Puerto Rico.

So, it wasn't only the explosion of the U.S.S. Maine to stir war fever. It was all of these factors combined.