I have same issue, but need to set country to US, here is how I fix it:
add_action('woocommerce_add_to_cart' , 'set_country_befor_cart_page');
function set_country_befor_cart_page(){
WC()->customer->set_billing_country('US');
WC()->customer->set_shipping_country('US');
}
Hope it will help.