Sugar is needed for yeast to raise the dough. It's common everywhere not in the US alone. I'm in Europe and most bread has sugar added during preparation. Small amounts but still sugar.
Added sugar is not necessary for yeast. The yeast is breaking down and using the carbs naturally present in wheat. The simplest breads, like french baguettes, are only made with flour, water, salt and yeast. Sugar is added to many commercial breads because it can make production easier and more consistent and sell more to consumers, but it's not added because it's necessary.
Ok, of the carbs in white bread here there is 0.6% sugar. That's completely negligible and now what I'm referring to at all. I am talking about added sugar where it will be 10-20% of the carbs in the white "bread" (I consider that pastry :D).
I think people are talking about adding sugar for taste, beyond what the yeast can metabolise, which is common in US food culture but not generally elsewhere.