tedster - 12:46 am on Sep 26, 2010 (gmt 0)
Is your domain one of the international TLDs - such as .com, .org, .net and so on? If it is and if you have backlinks from US sites, you should do OK.
I'd say only set the geo-targeting in WMT if you really don't want anything BUT US traffic.
Are you currently having a problem you're trying to diagnose?