I came across a good summary of these requirements a while back. Unfortunately, I can can't find it now, but I can say there are definitely laws regarding this in the US, but they vary by jurisdiction. Some jurisdictions require 2 single-occupancy bathrooms to be labeled gendered, while some other jurisdictions require 2 single-occupancy bathrooms to be unisex.

P.S.: While not what I was looking for, I was able to find this Reason article that talks about the issue: http://reason.com/archives/2014/04/11/gender-neutral-bathroo...