Nuneatonman - no problems at all in the USA - I was there two years ago, and security had no probs - just BA who were very jumpy because that was the exact time of the shoe bomber Richard Reid.
You will of course need an adapter for local power, and depending on the make of your machine, you might need to change the fuses. I found no problem using my CPAP in trains with power points adjacent to the seat, even in the daytime, and nobody gave me a second glance ........... jet lag!!
Jojo, yes it's the same plug - two pin round, but you might find that a universal adapter is the best way to travel ........ oh and an extension lead because often plug sockets are across the room from the bed .... not wanting you to get electrocuted while you sleep!!!