I am not sure what else may need to be changed without testing, but you can try changing the file:
/includes/functions/functions_customers.php
and add the code in RED:
Code:
if ($country == '') {
if (is_array($address['country'])) {
$country = zen_output_string_protected($address['country']['countries_name']);
} else {
$country = zen_output_string_protected($address['country']);
}
}
// bof: turn off country for matching country
if ($address['country_id'] == STORE_COUNTRY) {
$country = '';
}
// eof: turn off country for matching country
if ($state != '') $statecomma = $state . ', ';
Then try a making a test cart and check the Shipping Estimator, checkout_blah_pages, Admin orders, My Account pages and see if this one change manages everything on new orders ...
I am thinking this is not going to manage everything off the top of my head and that perhaps the new address_format on Canada and editing the address_format used for the United States might be the better choice ...
But, again, I have not tested this to tell you what all might need to be done ...