IB is different as it used to have a hub at MIA transferring pax between flights to the rest of central america (and also operated short-haul aircraft, A320s if I remember right, on some of those routes). So it had a business presence in the US that is different from an airline flying to/from the US. None of the other airlines you listed had flight operations that originated in the US. Rather ironically the MIA hub is dismantled now due to poor connection performance (pax had to clear US immigration and it took too long), however the corporate structure remains.