In Europe the common metric is l/100km. 35 mpg translates to a little above 6.7 l/100km, which is good - average for a car in Europe (average is 7.8l/100km = 30mpg). I guess today there is a smaller difference in fuel efficiency. This is for gasoline, not diesel engines.

US cars are a bit bigger than european or asian models, so they are probably a bit heavier. Still, I think fuel efficiency is pretty optimized in all modern cars regardless of where you live.