It's gotta be Mexico in the West, whether you go with the tiebreaker the standings app is using (net points in division games) or the current NFL tiebreaker at this step:
Strength of victory (the combined won-lost-tied percentage of all the teams that a club has defeated).
In other words, the power points/opponent win chart tells you this. Mexico beat teams with more wins, hence a higher win percentage, so Mexico is your AFC #4 seed.