My one and only encounter with an American border guard was enough to put me off for life! traveling on a UK passport and indeed simply changing planes UK-LA-NZ hop was awful.
Some moron with a gun grunted at me, finger printed me and photographed me when I entered America, just for the privilege of leaving America, it was outrageous!
I will never pass through that country again, I now take the HK route. I do hope you have the right paperwork for them because it wouldn't surprise me if they leaned over and bit you, where do you find these guys?
I guess I got off easy, my friend was stopped, placed in a large glass box for 15 mins then just as randomly released.
I note someone said you have to remember they are working for you, well I'm glad they don't represent me, what an awful way to treat a visitor, it left me thinking America, ha you can keep it!
The face presented at your airports is such a stark contrast to the Americans I know.
Bob