Is oh way to have the country default to United States? This website only ships products do the United States so there's no reason to make the customer select from a list of just one country.
Under Configuration/Countries unpublish all countries except USA. Note: do not delete the countries as they may reappear on the next VM upgrade.
You can preset the country value in the country field, it's the country ID
You can find the ID in the virtuemart country list
Perfect, putting 223 in the Default field of virtuemart_country_id worked.