Calculation request for USPS shipping service fails to US Territories

Steps to reproduce:
1. Set up USPS as a shipping option
2. Create an order with a shipping address in Puerto Rico or Guam
3. Calculate shipping rates

ACTUAL RESULT:
AJAX request fails with 500 internal server error

EXPECTED RESULT:
shipping results show up

checking out the code, this seems to be hitting an unhandled code path:
ubercart/shipping/uc_usps/uc_usps.module, lines 374 - 381:
if (strpos($method['id'], 'intl') && ($destination->country != 840)) {
// Build XML for international rate request
$request = uc_usps_intl_rate_request($ship_packages, $orig, $destination);
}
elseif ($destination->country == 840) {
// Build XML for domestic rate request
$request = uc_usps_rate_request($ship_packages, $orig, $destination);
}

note that 840 = country ID of USA
so in our scenario, the shipping $method['id'] is usps, and the country ID is (E.g.) 630 (Puerto Rico), so neither the first nor second branches match, the $request variable is never assigned and the HTTP request for shipping quotes fails.