Looking at the events that led up to the start of World War I, it seems like it would have been strictly a European affair. The US seemed to be content with just isolating themselves to the Western Hemisphere. What were the interests that the US was trying to protect? Was it just because their allies in UK and France asked for aid?
Whilst more can always be said with regards to the development of geopolitical arguments which contributed to the decision by Wilson's government to join the war in April 1917, these three older writeups should be of some interest to the question at hand - as there were of course, other reasons which must be taken into account for the US entry:
Note that these posts in of themselves have links to other relevant discussions on AskHistorians, so get ready for a fair bit of (fun) history reading as you delve into this most fascinating of historiographical rabbit holes.
Feel free to ask any follow-up questions about what is discussed in any of the linked posts, and hope this helps!