Not sure there's a correct answer. I could argue the U.S. adopting any of the three available positions (U.S. stays out, U.S. sides w/Germany, U.S. sides w/GB).
Given Washington's advice to avoid entangling alliances maybe staying out of it would have been in keeping with U.S. foreign policy since its inception. But by the late 1800s many in the U.S. saw the U.S. as THE emerging global power and were keen to do something to cement that status (Spanish-American War being Round 1 and U.S. involvement in China (think,
Boxer Rebellion) being a quick following Round 2).
Why side with Germany? Well, the U.S. probably had far more anti-GB folks (Germans and Irish) than pro-Brit. But Germany didn't seem to offer much and had as equally a bad rep as a colonial power as the others on the Triple Entente side.
Why side with the GB? Especially since forever GB was a thorn in the U.S.' side (Revolution, 1812, Oregon, Civil War, etc.). But Wilson was pro-British & anti-German. And GB did have a tradition as a liberal democracy while Germany's political tradition seemed quite un-American. So while I can see why the U.S. entered the war on the side of GB it still doesn't answer why the U.S. even entered.
From the State Department historian:
The precise reasons for Wilson’s decision to choose war in 1917 remain the subject of debate among historians....
Go here:
https://history.state.gov/milestones/1914-1920/wwi
I concur with this assessment. The
Lusitania sinking was tragic, but the Germans were probably correct that it was carrying munitions. Further, the claim that the U.S. had to go to war against Germany because Germany was resuming unrestricted submarine warfare and reneging on the
Sussex Pledge seems disingenuous: the Germans did so because the U.S. was already violating its neutrality by supplying GB. And yes, the
Zimmerman Telegram was a big deal, but I can't help but wonder if it was played up (and other things played down) to get the public on-board with what Wilson had already decided to do (and was just waiting for the right time to pull the trigger).
When war was declared Congress stated that we should go to war to make the "world safe for democracy." It seems clear that there was momentum to get the U.S. out on the world stage and going to war was the way to do it, but the millenarian mindset that gave us "make the world safe for democracy" meant entering the war on the side that wasn't Germany was probably a foregone conclusion.
The irony, of course, was the eugenics angle. Wilson was a staunch supporter of eugenics and of the two sides the U.S. could support it was Germany that was the more enthusiastic of the Master Race crap Wilson espoused (in fact, Nazi Germany made a big deal of pointing out that one of its inspirations wrt eugenics was Wilson and later U.S. policies in the 1920s!).
There is a possibility that our involvement in Europe in WWI was done to set more favorable conditions in the Pacific. We were expanding our Pacific "empire" and knocking off Germany would help our position there (we didn't have any real interest in Africa and German interests there, but getting Germany out of the Pacific might be helpful?). Not sure how much that played a role, but still perhaps worth considering.
So...complicated.
Always glad to learn more if anyone holds to a different theory (why I liked
@GURPS posts).
FWIW
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