I am not quite sure what SAT score is needed for someone from the USA applying to McGill. I do know several people (including me and a daughter and a few others) who got in with SAT scores ranging from 1410 to 1490. We all had GPAs that were pretty close to yours.
Just up the street from McGill is Concordia University, which is also quite good and is a bit easier for admissions. Concordia students can take a few classes at McGill. The only Concordia student who I know who took advantage of this said that the classes were more difficult at McGill. The two universities are close enough that at one point we rented a hotel right between the two and walked to tours at both of them on consecutive days.
The only other English language university in Quebec is Bishop’s, which is relatively small and in Lennoxville, which is right next to Sherbrooke. We toured Bishop’s and liked it quite a bit. They do have a department of “environment and geography”. McGill will of course be far better known by employers in the US and McGill is also very good for environmental science. I do not know anything about geography as a major.
My vague recollection is that McGill is likely to be under your budget of US$50k per year, and that Concordia and Bishop’s are both likely to be slightly less expensive still (unless you have dual citizenship, in which case they will all cost a LOT less). I have not checked the prices recently however.