Please do the following.

• In the location bar, type about:config and hit Enter.
  
  
• In the filter at the top, type: keyword.URL
  
  
• Double click it and remove whatever's in there and replace it with http://www.google.ca/search?q=
  
  

The URL to add in "keyword.URL" becomes a link in this post, so right click it and choose "Copy Link Location" to copy it to the Windows clipboard. Then hit CTRL+V to paste it. Saves you having to type the whole thing.

To reset your home page, do the following.

• Go to the site you want to set as your home page i.e. http://www.google.ca
  
  
• Click the orange Firefox button and go to Options | Options | General
  
  
• Make sure it says "Show My Homepage" in the first dropdown menu.
  
  
• Click the button called "Use Current Pages" to set the homepage to the one you have on the screen.
  
  

After you complete the above steps, install this add-on to prevent another search engine from modifying your preferences: https://addons.mozilla.org/en-US/firefox/addon/browserprotect/

In addition to the above:

Firefox 4 uses a new build-in home page called about:home with a Google search bar on it.
That about:home page only shows some snippets and has a button to restore the previous session if applicable.

Using the Google search bar on the about:home page should still open results of the local Google site in the country where your IP locates you.
If that isn't the case then try to clear the Google cookies.
if you want a home page with extras then set another page as the home page like www.google.ca or www.google.ca/firefox that is used in Firefox 3 versions.