I think the service roles and distinctions for the Army and Marines are still applicable in those cases. A sustained light campaign is still the purview of the Army, but the Marines’ early arrival can resolve a (very small) crisis contingency or buy time for the Army to field more light forces.

It really comes down to viewing forces along an expeditionary-campaign spectrum. The USMC occupies a fair portion of the spectrum on the expeditionary side, while the Army occupies the entire spectrum but dominates the campaign side.