if you don't have time, there is no point in scanning. well if you want to find US Socks, then start leeching a bunch of SOCKS and seperate them by country as USA and test the US socks.. you wll get what you are looking for.
I found sumthin funnie
http://stayinvisible.blogspot.com/2007/07/socks-proxy-tools-how-to-scan-socks5.html