Upon Render Remove Countries From DropDown List

Upon Render Remove Countries From DropDown List

Hi, I have a dropdown list of countries used to select which countries I'll ship to.

I really only need it to be United States and Canada.... but the list of options includes about every country there is.

I cannot alter this list, there is a template tag that simply spits out the following code when the page renders (list shorted for ease of display)

<select name="billing_country" onchange="document.billing.action='checkout3.asp?step=3&amp;action=updatecountry';document.billing.submit();" class="txtBoxStyle">
<option value="AF">
Afghanistan
</option>

<option value="AX">
Aland Islands
</option>

<option value="AL">
Albania
</option>

<option value="DZ">
Algeria
</option>

<option value="AS">
American Samoa
</option>

<option value="AD">
Andorra
</option>

<option value="AO">
Angola
</option>

<option value="AI">
Anguilla
</option>

<option value="AQ">
Antarctica
</option>

<option value="AG">
Antigua &amp; Barbuda
</option>

<option value="CA">
Canada
</option>


<option selected="" value="US">
United States
</option>
</selected>

I need a method of removing all the choices from the list except




United States and Canada so only those two can be seen when the list drops down.

Can this be done?