Pretty much this, yes. That and their load time made them pretty terrible for any sort of normal campaign. They really where a few tens of yards more accurate, and that with the myth that the entire war was fought with guerrilla tactics is probably where the "Americans where expert marksmen" myth came from, though.

In it's own way, this contributes its own additional disadvantage- The American's equipment was by and large 'whatever they could get', which makes organization among troops even more challenging than usual.

I've noticed that people really don't understand just how poorly the American army fared before the French stepped in and helped us organize and contributed any degree of actual military experience. Which makes me laugh because of how much most Americans today seem to dislike the French.