In many countries they have smaller servings - but it's typical to eat 2-3 servings. In the US we often have larger servings (equivalent to 2-3 servings) but only eat the one.
Having traveled quite a bit, the largest discrepancy in serving sizes I've noticed is that the US really likes drinks. Especially sodas and especially 60oz sodas. Everywhere I go gives me a "kids sized" cup of water to down with my meal...
Maybe the parent comment is counting the salad, the soup and the dessert?
But these are not "servings" as the OP was talking about, i.e. for the same dish (main course) that you would get 2-3 servings, something we don't do normally in Europe (perhaps only in big celebrations like Christmas).
In Australia, going out to dinner usually means two or three of an entreee (starter), main and dessert.
Fast food portions are huge though - in the US my girlfriend and I would get a burger each and share a small chips and drink.