Well, the corrupt incompetent hacks at CONCACAF have a page for
Champions League Regulations on their website. Let's see what it looks like:
View attachment 5330
So we have nothing to go on except Wikipedia, which says: " If a Canada-based team occupies any MLS-allocated berth, or any U.S-based team qualifies for the Champions League by more than one method, the Champions League place is allocated to the U.S.-based team with the best MLS regular season record which has failed to otherwise qualify."
To me that says that if the top team in the East is Canadian, then the US team with the next highest regular season point total in MLS -- regardless of conference -- gets the spot. That's also true for the top team in the West or MLS Cup Winner.