Been playing for almost 20 years. Rugby in the states has gotten a lot better. We're behind skill wise compared to Tier 1 Nations (Argentina, Australia, New Zealand and South Africa) and even some of the Tier 2 Nations (Fiji, Samoa, Tonga..imo). But we have some great athletes
Yes, this is due to the brain no longer having to work/provide power to that sense. The areas of the brain get rewired and put to work processing other senses.