For the USA she had to take the written test, she did not need to take the driving test after presenting the Cambodian license.
I have no idea if she was allowed to drive here on her Cambodian license, I was told yes at one motor vehicle location, no at a different location, yes on the phone and then no on a second call. We just decided to wait until USA license came in instead of risking it.
She definitely likes driving more in the US, less cutting each other off and no ignoring laws. Plus you get new cars here without getting destroyed in taxes.