To invade this city an army has to drive by a U.S. military base. Another significant obstacle on the invasion route is the Qatar Aqua Park. For people living in the country there is probably some concern about how the U.S. would react to an escalation of the current blockade by Saudi Arabia.
A card that has not been played yet is Qatar shutting off natural gas shipments to UAE. Towers of ilium puts the odds of a peaceful resolution to this situation at 75%.