A Google Webmaster Help thread has a webmaster who has a ccTLD, specifically a .com.au (Australian top level domain) and he is concerned that over the past four months or so, his US origin traffic from Google search has spiked.
He said, "Its weird because for the past 4 months we are getting huge impression from United States even though our domain is com.au."
The concern is that he is not targeting Australian searchers any more and something was reset.
Google's John Mueller responded that this is not the case, ccTLDs such as .com.au do not need to be configured in Google Webmaster Tools, they are automatically geotargetted for Australian searchers.
It is just a bonus that this site is getting US traffic but it should not negatively impact the Australian searchers, John implied.
John wrote:
I generally wouldn't worry about something like this. It looks like you've found the queries where these impressions come from -- you also see the ranking there (when I check here, it's mostly on page 4-8 of the search results, so not really that visible).If you have a .com.au site, then you don't need to worry about geotargeting.
Forum discussion at Google Webmaster Help.