OK - based on what you said in his profile, he's like to be Canadian Army, and World War I - I'll start with that and see what emerges...
So looking at these two photos, yours and the one on the other web page, they look very similar. Belt clasp the same. uniform and collar the same, rank the same - seems likely this is correct.
So the arm stripes - typically the top stripes are rank (I think I see 3 stripes and no rocker - I believe this is Sergeant) and the bottom one (I think I see 4 stripes - called Service Chevrons) relates to time involved in combat. 4 would indicate 4 years, I think. The badge on his shoulders indicates something - in the US Army it's generally the unit you were with. Not sure how the Canadians did this. Their might mean rank. The one on his collar usually indicates in the US Army what branch of the military he was with. The image is just a bit too blurry to decipher.
If you can interpret the badge, you might find it in this link.
Amusing... so lower on the page, it says the Canadians adopted the British style of uniform a bit later, but his is clearly Canadian (note the turned up collar).
At least these are my best guesses. Sergeant - 4 years in combat (awarded at the beginning of the year in combat, I think, so between 3-4 years is how that works). And the rest is still a bit of guessword.