The Gulf of Hormuz controls the maximum outflow of oil in tankers to the world. It is important to keep the sea lane open and hence the US 5th Fleet and an air base is located there, apart from that, also influencing strategically the Arab neighbourhood as also to keep their nose clean. Hence, Bahrain is important to the US geoploitics. If the monarchy falls, then the US will either have to intervene or quit if the new dispensation is not pro US. The danger is there since the majority population are Shias and they have a fraternal equation with the Iranians. And Iran Govt are anti US. Tough tittie!