The proposition USW led to U.S. entry is mistaken. Recall the Zimmerman telegram.
A lot of people (and writers) say that, and it has come up on the board before. But take a look at the period article from the New York Times Feb-3-2017 (before the Zimmerman telegram came out), and other articles from around then.
https://archive.nytimes.com/www.nytimes.com/learning/general/onthisday/big/0203.html#article
It sure implies the President has a lot of leeway to do whatever he wants, a couple of messy incidents on the high seas and we are probably in regardless of Zimmerman. (perhaps with less votes in congress than in OTL, and a delay over OTL helps Germany). I get the impression, Zimmerman made it politically too easy, vs a little had but doable to get the USA in.
(of course it may be like a strike vote, the Kerry I was before it before I was against it thing. the USA wants to look united, and ready to war, even if its not really, but its hard to turn that off in democracies)