I took a quick look in their source code, and it looks it's just an AJAX call to a PHP script. The Javascript function called:
function setCountry(e)
{
rcode = e.toUpperCase(), serviceStatusSpinner(!0, "Saving New Settings..."), window.setTimeout(function ()
{
$.ajax(
{
url: countryUrl,
dataType: "jsonp",
data: {
code: e
},
success: function (e)
{
h && (serviceStatusSpinner(!1), rcode == e.current ? (showBar("dialog3", "country-set"), $("#messages #new-country").text(e.current_full)) : showBar("warning1", "country-set-error"))
}
})
}, 1e3)
}
And the countryUrl variable points to
http://realcheck.unblock-us.com/set-country.php