I've always assumed that's either the corn syrup or something else that's in the American version, because I swear growing up in Italy I never noticed this.
Haven't done a side-by-side comparison, though, so maybe it's just my memory of my childhood tastebuds.
I live in France and there definitely is this feeling. I may be biased, because I only drink coke zero, which has a distinct "dryness" to it wrt other sodas. However, it's the only non-zero soda where I notice this feeling.
Children have a much more sweet tooth than adults, so it may be the reason you did not notice it, as it would not necessarily register as bothersome. I liked to bite into direct sugar cubes as a kid, which I would definitely not stand today.
Haven't done a side-by-side comparison, though, so maybe it's just my memory of my childhood tastebuds.