Thank you for the correction.

The wording is extremely unclear, and AA's intended meaning is opposite of how one might read it. That is to say, as written on AA's website, if you are flying Alaska Airlines in a premium cabin, you would get Admirals Club access when flying to Canada, the Caribbean, and Mexico. Those flying AA would only get access flying to Mexico City.

Third party websites indicate that AA's interpretation is the opposite of the above with Alaska Airlines premium cabin travelers only getting access flying to Mexico City. (I shouldn't have to rely on a third party source for this information.)