The Pacific Campaign featured the strategy of "Island Hopping" heavily, in which small islands would be captured as staging grounds and airfields from which the US could project power, eventually within reach of the Japanese home islands. Marines were trained for amphibious warfare, which island hopping would necessitate. Beyond a few instances, amphibious warfare wasn't a huge aspect of the European theater, in which case the Army would be adequate for the job.

There were marines in the European theater. Each battleship had about 100, each cruiser about 80 manning various guns and providing for landing parties.

Their first action was taking over Iceland from the British who had invaded that neutral country. About 1,000 lucky marines guarded the place until they were relived by army troops.

After that you have to go all the way to the 1944 invasion of southern France (Operation Dragoon). Ike ordered that an objective be reserved for the fleet's marines. About 100 men, led by a captain captured the island of Retonneaux in Marseille's harbor. Not a shot was fired.

In fact, I cannot recall any marine being shot at (on land) in any serious way in the European theatre.