Also a large number of Highland Scots served in the British Army. For instance, The Black Watch.
And then there were the American Indians who joined both sides; some fighting with us and some with the Brits, against us.
Both sides were diverse...which should make today's far lefties a happy bunch; though they're appartently NEVER happy about anything.
When the Jacobites, who sought to restore the Stuart dynasty in Britain, were crushed by the government in 1746, many of their partisans from the Scottish Highlands fled to the Carolinas. Oddly enough, when the revolution broke out in 1775, the offspring of these transplanted Highlanders mostly sided with King George, who was of the Hanoverian dynasty against whom their fathers had fought. Unfortunately for them, they again chose the wrong side and were defeated by the revolutionaries early in the war.