Omnibox NCR

This extension, will force using google.com (aka Google No Country Redirect) when you search in Google Chrome Omnibox. If you travel a lot, or you just care about privacy and use proxy to hide your real IP from another country, imagine you’re in China and using a Japanese proxy, Google always redirects you to google.co.jp when you search in Google Chrome Omnibox. This extension could definitely make your browser stick with google.com. Under the Hood This extension simply replace the URL you request before onBeforeRequest to google.com, no additional internet request will be made since the replace process will be done in 307 Internal Redirect.

Screenshots from Chrome Web Store