Why was the U.S. Interested in Saddam Hussein and his Invasion of Kuwait?

Strategist, statesmen and the general public quickly came to understand that the United States had significant interests in making certain that Saudi Arabia was not conquered by Saddam Hussein and his regime. Having rolled over Kuwait, Saddam already controlled over 20 percent of the world's oil reserves. Saudi Arabia contained an additional 20 percent. Since the world economy was primarily driven by fossil fuels, what Saddam could do with these resources could have been detrimental to both the American and world economies. 

Besides economic factors affecting the daily lives of every American, there were other considerations, even more important with respect to Saddam, such as his invasion of Kuwait that had perpetrated many atrocities on the Kuwaiti people, from summary executions, to confiscation of property, to the torture and degradation of individuals. Such crimes could not be ignored, and Americans had every reason to expect that this kind of behavior would continue and even accelerate should Iraqi forces move into Saudi Arabia. 

Further, Saddam and his regime had been vigorous in developing weapons of mass destruction. CIA and other intelligent experts estimated that Saddam was on the brink of developing nuclear capability and likely had a biological weapon's capability. There was no question that they had chemical weapons. Moreover, Saddam showed that he was ready, willing and able to use these weapons, as he had even done so using chemical weapons on villages within his own country in order to put down the Kurdish independence movement. 

Economic sanctions had failed to keep Saddam from committing atrocities, they had failed to keep him from developing weapons of mass destruction, they had failed to keep him from invading Kuwait. A majority of Americans understood that military force was not only justified, but it was absolutely necessary. 

References: http://www.indepthinfo.com/iraq/