Hessians in the Southern Campaign
Most of the troops involved in the Southern Campaign appear to be British and Loyalist units. Why weren't more Hessian troops used?

Have you looked at Guilford Courthouse scenario? :)

Ezza, The conventional wisdom is that the Hessians were poorly regarded by the British allies after their performance in the first two major campaigns (1776 and 1777) and were left in garrison in New York City from then on. In fact, quite a few Hessian - and other German - units "went South" for one or more years, although almost all served entirely as garrison troops. All the more surprising because the Hesse Cassel contingent had a special (and unique) condition of service, namely that they had to be commanded by one of their own generals in the field. I'm not sure how the British got round this officially, but in practice several regiments became "isolated" among British and Loyalist corps in various garrisons and hence came under British generals by default. A couple of jaeger companies served in the South, including one under Ewald (can't recall the other company OC's name off hand); I seem to recall a small mounted jaeger unit at Charleston - after its capture - that acted as a recce/provost/deserter tracking unit. The 1st, 2nd and 3rd Grenadier Battalions, and the Musketeer Regiment Prinz Carl all served at the siege of Charleston in 1779-80 before returning to New York City. The Musketeer Regiment von Bose, the Grenadier Regiment d'Angelelli (ex-Rall), and the Garrison Regiment Wissenbach/Knoblauch, all served in East Florida in 1778, then defended Savannah the following year, before joining the garrison of Charleston. Von Bose served with Cornwallis in the Carolinas and Virginia, ending up at Yorktown. D'Angelelli and Knoblauch remained in Charleston until it was evacuated in 1782. The Fusilier Regiment Erbprinz served in Virginia under Arnold/Phillips, and then garrisoned Portsmouth before joining Cornwallis at Yorktown. The Fusilier Regiment von Dittfurth and the Garrison Regiment von Huyn served at Charleston from the siege to the evacuation in 1782. An ad hoc "chasseur" (light) company drawn from some of the regiments of the New York garrison, served at the siege of Charleston, then returned to New York City (where it was disbanded). The 2 Anspach-Bayreuth regiments, with their jaeger and artillery companies, served in Virginia and at Yorktown. The (3rd) Waldeck Regiment served at Pensacola in West Florida from late 1778 until the town fell in May 1781.