The meaning of this question is not completely clear. I see two possible meanings. I will give an answer for each potential question.
First, you might be asking whether this war was anything more than a war. For example, we can say that the Civil War was more than just a war because it was fought (in part) to end slavery in the United States. We could say that World War II was more than just a war because it was fought (in part) to free the world from the threat of Nazism. These wars had (one can argue) higher purposes and therefore they can be seen as more than “just a war.”
If we look at the question in this way, I would argue that the Spanish-American War was more than “just a war.” It was fought, in large part, because the United States wanted to be seen as a more important power in the world. In other words, Americans of the time would have thought that it was aimed at a higher purpose. It was not simply about fighting Spain for the possession of some islands. Instead, it was about allowing the US to take its rightful place among the great nations of the world.
Second, it is possible that you have mixed up the words in the question and you might be asking whether this was a “just war.” In other words, was this war moral and was it right for the US to fight it? I would argue that it was not. You could argue that the war was just because the US was fighting to liberate Cuba from Spanish oppression. It is surely just to fight to make a colony become an independent country. However, the conduct of the US after the war shows that our motives were less noble. Through this war, we came to dominate Cuba. We did not colonize it explicitly the way Spain did, but the Platt Amendment essentially gave us control of Cuba. Through this war, we came to colonize Puerto Rico, Guam, and (after a bloody war against natives fighting for independence) the Philippines. In short, this seems to have been a war that was fought to give the US more power and prestige. Whether this is a just cause for a war is a matter of opinion. My own view is that this is not a just cause and the war, therefore, was not a just war.
Personally, I think The Spanish American War is not a "just" war because McKinley declared war on Spain. Spain didn't want war because they knew it wasn't their fault that the U.S.S Maine exploded. Americans wanted war because they thought it was Spain who bombed the U.S.S Maine. McKinley declared war because Spain caused many Cuban deaths. He also wanted all the problems occurring in Cuba to end and to have peaceful trades between U.S & Cuba and other countries, again. The Imperialists argument against the Spanish American War was Senator Beveridge think God prepared us. God made certain people mastering organizers to create a system in an area of pandemonium . He made us have a stable government, where Americans attain new territories and people treated them bad. Beveridge believed that if it wasn't for god, the world would've collapsed. Alfred believes that many countries needs Americans to think beyond and to think of better skills or techniques, so their power can influence other parts of the world. If Americans don't look outward, than they will collapse.