For unique product identification and barcoding,  I understand that
European trading partners use a 13-digit EAN code and the American
companies use a 12-digit UPC code.
My question:
What typically do European companies do that trade in the US? Do they
use two codes, and when they trade in Europe they use the EAN, and
when they trade in the US, they also mark their products with the UPC?
 Or are American companies able to process the 13-digit EAN also? Any
statistics on this?