Is there an easy to use a firmware upgrade to allow non-USA Xooms to be upgraded to the USA version and then receive the USA upgrade to ICS?
Yes, there is! However, before I go to explain how I did it,
please beware that you will
void your device warranty as you will have to
unlock the bootloader in the process. That's the scary part out of the way, although one final caveat, you may also "brick" your device.
I had a pretty smooth experience unlocking and flashing the US HWI69 Retail ROM (V 3.01) onto my UK Xoom. The steps I took were pretty well explained by others whose instructions I found by simple googling the subject. Here is hwat I did:
1. Download and install the Android SDK Starter Package on you PC/MAC from here
Android 4.0 Platform Highlights | Android Developers, run the SDK and update any packages the program will identify as updatable.
2. Download the US HWI69 Retail ROM from here
MOTODEV > Products > Device Software - if asked to sign into your developer account simply create one and reply to Moto's verification email. After that you can download the package.
3. Unlock your Xoom bootloader first (again, this will invalidate your warranty!!!) and then begin the process of flashing the US stock ROM onto your Xoom. The simplest instructions I found were these here
The technology preview
4. When you have flashed the US ROM then just setup your device as per ususal and establish your WiFi connection. If you don't get a notification for the first update then go to system settings > about tablet > system updates. This will find the initial update and ask you to confirm to install. You'll need to do this process 4 or 5 times after which you'll end up with ICS 4.0.3 on your Xoom.
5. One final thing, you'll have US regional settings only so you need to change your input and keyboard settings to incorporate "UK" settings. Foir this tpo work properly simply go to the market and download an app called morelocale2. You'll easily figure out the add UK settings. Voila - ICS goodness. P.S. if you want to go back to the original UK stock ROM for any reason then follow these procedures minus the bootloader unlock, and flash the H.6.2-24 For Retail Europe build back to your Xoom- you'll be able to obtain it from the same place as listed under item 2. You can also relockj the bootloader. This is not rooting the device.