Probably due to their technology: http://www.google.com/technology/pigeonrank.html -Hank

Google appears to have the capability to georeference their index by country and possibly with even finer geographic granularity.

I noticed that they are now redirecting users to country specific versions of their web page which appears to be done through the various IP address to location tools.

Given that Google *seems to know* where the user is, and where the web pages are, perhaps they are now including geographic relevance in the search engine relevancy metrics.