As I mentioned in another post, one of my ancestors came to America following Culloden, because he was on the losing side of the battle. It's possible he continued to wear highland dress while tramping about the mountains (he eventually married himself a Cherokee lass, so that tells you what part of the frontier he was tramping), because he was proud of his origin -- but it's also possible he wore the same leather trews as other fur trappers and mountain men, because it was harder to get a suitable length of plaid here in the wilds, or because it was more suitable for the local terrain... remember that, in the 18th century, it was said a squirrel could travel from the Atlantic to the Mississippi without touching the ground.

So I'd bet you could justify wearing a great kilt for reenacting, as long as you're not portraying a military unit -- my great-great-etc-grandfather can't have been the only Highlander to come to the new world as a fugitive during the troubles in Scotland.