Raf, Tuppence worth from a Weegie, just do it. You will have a ball. I often wear the kilt in my home town of Glasgow. I have never had any dramas. People love seeing them and you will see other kilts. Derek is right when he says that you may get comments good or bad but so what? Its about you having an experience that you won't forget and as Grizzly says, you will get tourists demanding photos. There must be pictures of me all over the world! I even got mobbed once by japanese tourists when I went kilted to Llangollen in Wales. As long as you are dressed with pride and respect for the kilt and not like something from Brigadoon, you will be fine.
Scots tend to wear the kilt travelling in aircraft abroad in order to save luggage weight and space.
As for being American, If i saw you kilted in 'the dear green place' and discovered that you are american, then I would be proud to shake your hand then take you for a dram to welcome you home.

And by the way, wise advice from Jock. I served with the Army and the Royal Air Force. I didnt go anywhere in out in the cuds without Avon skin so soft. Its the only thing that works on the dreaded midge plague.