You need to pass success and error callbacks to the geoip2 methods. Try this:
geoip2.country(
function (response) {
if (response.country.iso_code === "US") {
document.write(hockeyAds[4]);
} else {
document.write(hockeyAds[5]);
}
},
function (error) {
// handle error
}
);
Also, this tutorial might help you understand the API: http://dev.maxmind.com/geoip/geoip2/javascript/tutorial/