It's about the same as PHL-AMS. At the edge of the envelope but doable.
on the topic of getting former Mexicana planes, except for the 2 767-300's the widebodies are all 20 years old according to AirFleets. Would do in a pinch, but don't know if they're worth the investment required to reconfigure to US specs. Maybe if US could get them with low enough lease rates.
Jim