Create a dropdown list with magento’s countries is easy :

<select name="billing_country" id="billing_country">
<?php
 $_countries = Mage::getResourceModel('directory/country_collection')->loadData()->toOptionArray(false);
 foreach($_countries as $_country)
 {
       echo '<option ';
       if($this->getCustomer()->getBillingCountry() == $_country['value']){ echo 'selected '; }
       echo 'value="'.$_country['value'].'">'.$_country['label'].'</option>';
 }
?>
</select>