In your scenario, it's likely that you were drafted. As Current et al. wrote in the text American History:

Only a national draft, (Wilson) insisted, could provide the needed men...he won passage of the Selective Service Act in mid-May. The draft brought 3 million men into the army; another 2 million joined various branches of the armed services voluntarily.

If you were part of that two million that volunteered, it's possible that you saw the propaganda sent around the U.S. by the Committee on Public Information after the 1916 election. This propaganda, like the British, focused on moral superiority over the Germans. German submarine tactics (particularly the sinking of the Lusitania for Americans) were considered barbaric, and the Allied cause in general was seen as one for democracy. "Huns" was a term commonly used in American propaganda to describe the German forces. [An example of such rhetoric can be seen here.] (http://multimedialearningllc.files.wordpress.com/2009/05/wwi.jpg)

In terms of raw financial incentive, there was a precedent for enlisted troops to receive bonuses for their volunteering in previous American wars. However, this ended with the Spanish American war when veterans did not receive a paid bonus. After WWI, the "Bonus Army" formed to march on Washington to receive their bonus pay, which was granted, as David Greenberg writes in "Calvin Coolidge", in 1924 when Congress allowed 500-625$ to be paid to the veterans. However, this incentive was largely after the fact and may not have had bearing on the initial enlistment of some troops.