I agree with Woodsheal. In my research I've uncovered nothing to suggest expatriate civilian Highlanders wore their traditional highland garb. From all I've seen, it appears they adapted the same clothing as worn by the colonials where they lived. I think even the Scots bonnet is far overdone in the reenactment community (and I'm one of those guilty of it at times).

Yes, there were several Highland regiments in both the French and Indian War and the American Revolution but they were soldiers wearing a uniform. And, as Woodsheal also pointed out, even they transitioned into breeches and leggings or trousers after a few years of campaigning.

As an immigrant Scot, you might have had a plaid stored by for special occasions, such as a wedding, but not for daily wear.