So this USA would also indulge in imperialism, even after the unpleasantness of the war with Spain, and expend men and resources to occupy Canada against a hostile population that was free to roam the hills, crossing into the USA?
Another factor against even a pro-CP USA entering the war.
Personally, I doubt we would see a the US enter the war on Central Powers side unless the British did something really extreme to provoke them, like firing on and sinking several US-flagged freighters that were trying to slip past the blockade and brutally butchering any of the crew that survived.
The great bulk of the US populace was content to let the Europeans fight their war without dragging the US into it so long as US interests weren't particularly threatened..