In the late 1890s, the United States was a very imperialistic nation. It had already annexed Hawaii and purchased Alaska, and its next interests laid in the island of Cuba. However, they had one problem; the Spanish owned that territory, and refused to sell it to the United States. Therefore, there was only one option to feed the still-young nation's hunger for more land; fight the Spanish. The war did not affect the economy at all, nor did the revolt going on in Cuba in the first place, and the United States fought a bloody battle for both sides, with their own troops being killed in large numbers. The entire war was also to gain popularity on the President's side, making it more of a political statement than a righteous battle, and the government did very little to even try for peace or any rational diplomatic communications. The United States was defnintely unjustified in going to war against Spain.
There were little to no economic reasons to fight the Spanish War in the first place. Cuba was simply a financial interest for the United Stated government, as was the philosophy of Manifest Destiny which they now sought to complete. Even the Cuban revolution against the Spanish didn't effect anything in the United States, despite its proximity to the country. As far as economy, it probably would have done a lot better had we not gone to war, for not as many resources and materials would have been wasted. Economically, there was no reson to go to war with Spain.
Morally, the war was horrendous. Troops were being sacrificed for the sole purpose of imerialism, when the United States was already a very large nation in to global picture. Had there been some wrong that the Spanish did to the country, then there would hae been reason to sacrifice American soldiers, but for the sheer interest of land and nothing more, aside from global pride, it was a very poor cause. On top of that, the war was being fought for political reasons as well. The Spanish were seen as an enemy for refusing to sell land, and now the government wanted to show its people that it could be strong, and raise support in coming elections. In this way, the government was merely throwing away American lives so that it could win popularity, and maybe even a bit of land as well. A terrible moral cause to fight a bloody war.
The United Stades also did very little to negociate with the Spanish, aside from offering to buy a large island that happened to be next to it. The Spanish refusal to sell it to America should have been enough, and even if they did need to get more land, they could have searched elsewhere instead of jumping to war. It was the most undiplomatic war fought, aside from possibly the Iraq War. This shows how hot headed and single minded the government must hae been in 1898.
The United States had absolutely no reason to fight the Spanish, aside from fulfilling an upshot and overblown thought that the United States "deserved" all the land it wanted. It was a political statement as well as an unnegociated and barbaric fight, and had no effect on the economy in the first place. In the end, the United States didn't even win Cuba, as it fought the war with the Cuban revolution. Instead it settled for the next best thing: three islands previously belonging to the Spanish. And if the spanish didn't own those territories, the United States probably would have annexed part of Spain itself. An unmoral, unorganized and bigotic war, for the sole purpose of raising praise and pride.