From what I understand, you are right that schools have opened up around the country/offshore and that residency spots have not really increased. I don't know the full details, but I know that residency is largely funded through Medicare and that this funding has not increased in a while (I think since the 90's), hence the lack of growth. However, there are still fewer graduating US MDs and DOs (definitely MD's, not 100% sure about DOs) than there are residency spots every year. Basically anyone who graduates in decent standing from a US MD & US DO will match unless they screw themselves over with a terrible match list/unrealistic specialty. The real losers in this change are FMGs and IMGs who try to get US residencies. In general, FMGs and IMGs get last licks at residency spots, so they will be the ones who have a harder and harder time matching in the US.
source:
http://www.nrmp.org/wp-content/uploads/2016/04/Main-Match-Results-and-Data-2016.pdf
TLDR: More schools, same residency spots more or less. Non-issue for US MD's and DO's who graduate in good standing and don't screw up application process, much bigger issue for FMG and IMG.