Does that expression work?
Does that expression work in American English - to be wet behind the ears at something , meaning to not have still experience at something ?
thank you for advance .

Question

Does that expression work?
Does that expression work in American English - to be wet behind  the ears at something , meaning to not have still experience at something ? 
thank you for advance .

Answer

It sure does!  Generally, in American English, we don't say "wet behind the ears at ___."  You might say, for example: "Oh Steve?  Yeah, he's doing great -- just a little wet behind the ears."

So we generally wouldn't say the "at ___" part.  That would depend on the context and the conversation topic.  It wouldn't be wrong to say the second part, just uncommon.