In the American Revolution, many of the Scots-Irish or Presbyterian Scots settlers were active participants in the Revolution, while most of the Scottish Highlanders in America were committed Loyalists. The political reasons for this were quite complicated, but even Jacobite rebels exiled to America generally took the British side in the Revolution, while one of the only Highland settlements to join the rebels (upstate New York's Argyll colony) was settled by the members of anti-Jacobite clans like the Campbells. Whether Scots-Irish or Scottish Highlander, Presbyterian religious faith was closely associated with support for the Revolution, but most Highlanders from regions other than Argyll were not Presbyterian.
Loyalist Highlanders in North Carolina staged a classic Highland Charge with drawn broadswords at the Battle of Moore's Creek Bridge, but it ended in disaster because the rebels had tampered with the planks on the bridge. Broadsword charges depend entirely on momentum and psychological impact to scare the enemy into retreating so he can be cut down from behind. When the Highlanders were slowed down by the missing (or, in some accounts, greased) bridge planks, they were gunned down by musket fire.
Highland loyalists in New York's Mohawk Valley had much more success with guerrilla warfare tactics as members of the infamous Butler's Rangers. In Boston, a Highlander who had been offering broadsword instruction to the local young men was forced to flee the city, after which he became a Loyalist officer. Because so many Highlanders took the Tory side, there was considerable prejudice against Scottish Highlanders in America for a time.