The biggest issue is that some american carriers have NON-TYPERATED co-pilots!!!!! [from airbubba]
Some of this is nomenclature. Until fairly recently, the U.S. did not have a P2 type rating (in Oz this used to be called a copilot type rating as I recall). A couple of years ago the FAA started giving P2 type ratings to FO's who had been through an approved course, usually the normal airline FO training.
Any U.S. type rating in the old days (more than a couple of years ago) was a P1 or command type rating. Only the captain on the unaugmented crew was required to have the type rating, which in airline operations would be an ATR, later ATP type rating as opposed to a commerical or Part 91 type rating.
The first officer was required to have a commercial pilot license with catergory and class endorsements but was not required to be type rated in the specific aircraft. Most airlines only typed the captain but a few, like Pan Am, went beyond and typed all pilots.
With an augmented crew at least one pilot on the flight deck had to have a type rating so for international ops, many or all of the FO's had the type rating whereas on domestic ops they usually did not.
I remember riding United ORD-NRT a decade or so ago on a B-744 with a captain and three FO's. Apparently the flight was under 12 hours and only required two FO's but a third was put on for contractual reasons 'to plot in Russian airspace'. Or so they told me.
Anyway, for international ops the U.S. now requires at least a copilot type rating for all FO's. I don't fly much domestic so I'm not sure if domestic FO's now need the P2 type rating, I don't think they do.