It probably also has to do with the size of our country.
I myself live in the Netherlands. I’ve done a lot (re)mapping in my area and that’s probably 100-200 square kilometers.
That would be a small spot on the US-map 
But if everyone does it’s part as far as he/she can (in it’s own area or on visits or holiays logging data and afterwards enter the data on OSM), the maps will get better.
In Europe it is indeed better mapped, but at the moment I’m on holiday in France and found out that there is also a lot of work to do by entering many local roads (with nice climbs for my roadbike).
Keep going the good work and itthe maps will be better everywhere.
groen_duiven