Here is information for both perspectives:
Justified
America was justified in going to war against Spain in 1898 because the US was trying to help Cuba become free from their current abusive relationship with Spain. The Spanish government consistently mistreated Cuban citizens. Since the US is so close to Cuba, geographically speaking, it makes sense that the US gets involved to help these citizens.
Not justified
The US should not go to war against Spain because they never did anything recently to harm American citizens. One of the main reasons citizens wanted to go to war with Spain was because they were accused of blowing up the US military ship the USS Maine. However, this was never proven. This shows that the US should not get involved in fighting the Spanish in Cuba.