It really has nothing to do with boarding---it's a show up time. Since you're in The Retreat, it doesn't matter anyway. You can arrive and check in when you want, then actually board when they begin the process.
Another country? Probably not. State? Who knows!!! I called last week, and the very proficient agent took care of my issue---BUT, a couple of times I heard a kid acting up in the background. Probably working remotely.