There is an obvious answer to my question but I don't know what it is.
When I am on my wired network and I use nmap to scan an external network nmap works fine. When I connect to my wireless network and scan the wireless network starting 192.168. nmap works fine. When I am on the wireless network and try to scan an external network nmap refuses to find anything. I have tried this on multiple wireless networks and while nmap will scan the internal network it will not scan external networks with non-NAT IPs.
There must be a simple reason but what is it?