REMEMBER: At present it is not possible to root a tablet which has been upgraded using this method. Once you update, you will loose Root access, which makes changing the region back to your original country impossible. Only use this method if you don't care that you will loose root.
While this worked just fine for me, I'm not promising it will work for others. Try this at your own risk.
Step 1. Install the ADB drivers using the instructions here
Step 2. Download and run the All-In-One tool from here
Step 3. Follow the on screen instructions to Root your Tablet. Once this is completed and the device has rebooted, open AIO tool again.
Step 4. Follow the on screen instructions to change your Region to US.
Step 5. Reboot your tablet and go to settings-About-System Update. It should prompt you to download the 4.0.3 update now.
Step 6. Download and follow the instructions on screen to update.