On a trip to Las Vegas a year ago I wore my black denim UK, I had no trouble when leaving my home town - while taking off my shoes security did say I might want to take off my belt, but I told them they didn;t want to see that.
The Vegas airport was a different matter, I set off the detectors so had to be wanded. Being in a hurry I missed a penny in on e pocket, had questions asked about the blood pressure med's in a plastic container in another pocket, took my socks off to prove my toe rings weren't dangerous. Then when everything was done, I was asked if I was scottish. After the no answer, I was asked why I would wear 'something like that'. Now being midnight I'm getting a bit testy so I answered his question with 'is that part of your job to ask why people are wearing a specific garment'. He didn't react to much, but to 2 other TSA folks with in ear shod where laughing to beat h...
With all that I suggest whole heartly WEAR you kilt.

Jack