It is real easy to switch to Google.com from Google.ca. Simply go to the Google.ca home page and to the right and under the "I'm feeling lucky" button you can use a link to take you to the Google.com home page. Once you are there set it as your default homepage and you will always be searching from Google.com and not Google.ca.

This should be the case for any geo-Google home page.

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You can lead a blonde to reason but you can't make her think!