Arriving late on this thread my first feeeling is that I should avoid any kind of US Warrant Officer in case either of us cause the other great offence by an incorrect exchange of compliments.
On reflection, I shall leave the rest of you to this fascinating debate and continue to use common sense in dealing with my allies. I would like to say that all the CW5s I have met around the US Army helo force have been charming gemtlemen and completely free of any inferiority complex brought on by encounters with confused Brits!