As everyone has already mostly mentioned, the 767 was designed to be used on transatlantic and transpacific flights. In fact, I believe the 767 was the first airliner with less than three engines to be allowed to fly extended periods overwater (ETOPS) way back in 1985. (FYI: ETOPS means Extended range Twin engine OPerationS... or my favourite Engines Turn Or People Swim).

Over 1000 have been delivered and most of them operate transatlantic or transpacific. Many flights are over 11 hours.

Also as mentioned, you will probably more notice the difference between AA & BA than the 777 versus the 767.