I had this problem too.
What I did to solve is, was find this file: https://github.com/PrestaShop/paypal/blob/df46f740003ca41a878441195fef52d52ef19c0c/express_checkout/process.php And change the line #284: $fields['PAYMENTREQUEST_0_SHIPTOCOUNTRYCODE'] = $country->iso_code; To: $fields['PAYMENTREQUEST_0_SHIPTOCOUNTRYCODE'] = 'PT'; //$country->iso_code;
For your case, I think should be: $fields['PAYMENTREQUEST_0_SHIPTOCOUNTRYCODE'] = 'US'; // $country->iso_code;