Did the British have a militia during the Revolutionary War or was it just the Americans? I know there were Germans on the British side.

The bulk of the British forces were regular army sent from Britain, supplemented by units hired from principalities in the German lands. Because Hesse was one of the larger German principalities involved, the Patriots collectively called them Hessians. These were regular soldiers basically rented out by their prince (or elector or margrave or whatever he was called — the ruler of that particular principality).

The British also recruited American loyalists to serve side by side with the regular troops. Some of these were definitely organized as militia — part-time soldiers who served only in their home county or province. Some of these units were quite large. The New York militia had 3,500 men under arms, plus a company of artillery and fifty dragoons. Smaller units were raised in Pennsylvania, New Jersey, some in the southern provinces. Most militia units engaged in non-combat activities such as repairing fortifications, patrolling streets of towns, and watching the coast.