I am also comparing US A&P system against EASA B1 & B2 system.
I find it that in general A&P covers EVERYTHING - turbine & piston engines, fixed & rotary wing, avionics - while EASA licensing is so specialized - mechanical for turbine engine fixed wing, piston engine for rotary wing, avionics etc etc.
Correct me if I'm wrong, but in the US, holding A&P & working in general aviation, you can sign for basically everything (trade wise - eg. one day you can sign for some one's Cessna 172, next day R22).
But I believe an A&P working in a 145 on large aircraft would probably require "specialist" training (eg. turbine engines only or avionics only), or as wrench1 says maybe a Repairman cert will do, A&P not necessary.
Another thing I noticed is when it comes to type course - In an EASA type course (eg. 737NG), they conduct "mechanical" or "avionics" course, but when it is FAA approved type course (eg. conducted by Alteon) there is no such thing as mechanical or avionics, it's only 1 course...