It could - and most probably would - rise up again, eventually. Rising up from the half-buried wreckage of modern civilization is easier than building it from scratch.

Not necessarily. To be blunt, we've basically exhausted practically all the useful non-renewal natural resources (ores, etc.) that a civilization could access with 1200s-level technology. They'd have to mine our ruins for metals and such - and much of it is going to be locked up in forms that are completely useless.