License fact.
To be able to work on a N-registered plane, you need to hold a FAA Mechanics license number. This is to do the work and be able to sign it of in the log book. The JAA/CAA license is worthless on a N registered plane, just like the FAA license is worthless on any other than N registered.
I have worked in the US, and hold both a FAA license and a JAR 66.
Hope this info helps. Have fun in the States.
Where are you going to, if I may ask?