gistfile1.php

<?php

/**
 * Defaults customer meta for shipping country to the good ol' US of A.
 *
 * A function like this could be really useful in defaulting to the country that is most commonly purchased from.
 * Or even to the base country of the store.  Sky's the limit, folks.
 *
 * @param  null $value    A null flag.
 * @param  string $key    The meta key being passed to the customer meta API.
 *
 * @return string|null    The meta value, or null, if unmodified.
 */
function zao_default_country( $value, $key ) {

	remove_filter( 'wpsc_get_visitor_meta_shippingcountry', __FUNCTION__, 15 );

	$current_value = wpsc_get_customer_meta( 'shippingcountry' );

	add_filter( 'wpsc_get_visitor_meta_shippingcountry', __FUNCTION__, 15 );

	if ( $current_value !== '' ) {
		return $value;
	} else {
		return 'US';
	}

}

add_filter( 'wpsc_get_visitor_meta_shippingcountry', 'zao_default_country', 15, 2 );