Hiroshima was strategic, as it was on an industrial center. Tactical is on a battlefield, as in troop concentrations or to deny a location for passing.
For the most part, with one exception. As quoted to me by a marine: "Marines Arrive Ready In Navy Equipment, Sir."
They also have Navy Corpsmen and Navy Chaplains. Of course, they are also part of the Department of the Navy, so I do not see the point really.
Tradition is important when it comes to getting results in a military conflict and the Marine Corp has a great fighting tradition. Something no amount of money can buy.