Why did the United States enter the Persian Gulf War?

What does this answer mean?

The United States entered the Persian Gulf War to force the Iraqi military from Kuwait. That's the answer USCIS accepts.

On August 2, 1990, Iraq invaded its small neighbor, Kuwait, and overran the country within hours. The United Nations Security Council demanded that Iraq withdraw immediately, placed economic sanctions on it, and declared Iraq's takeover of Kuwait invalid. It later set a deadline for Iraq to leave.

When the deadline passed, a coalition of countries led by the United States began Operation Desert Storm on January 16, 1991, starting with an air campaign. A ground offensive followed in late February, and by February 28, 1991, Kuwait had been freed. About 697,000 U.S. troops took part in the war.

The Persian Gulf War is also one of the accepted answers to "Name one war fought by the United States in the 1900s."

At the interview, say "to force the Iraqi military from Kuwait."