A couple of points
1. Actually - according to TM1-1 - 5% survives not 1 %
2. There were massive population pressures in 13th Century Europe (about 5 kids per mother) so it doesn't need a high technology. Admittedly, waves of plague soon dealt with that problem, but
3. my (possibly optimistic idea) is that - in the ccanon time-frame - the population of North America is 20 to 25 million and is enough to support trade routes
I lay out some ideas for other population figures in
this new thread