I recently came to Ireland and brought my Xbox with me. I bought an adapter for it but I'm not sure it will work with the Xbox or fry the power brick. Here is the link.
I believe it is not compatible. Ireland uses the European standard of 230volts (or 240v) 50Hertz. The US uses 120v 60Hz. Looking at http://support.xbox.com/en-US/xbox-360/console/power-supply it looks like the xboxes ship with a different external PSU for each area. If you plug a 100v PSU into 240V power it's likely to blow up. Your best bet is to buy a new external powersupply.