No need to go elsewhere... I just used my One XL in Germany to great effect. You'll need the TomTom software loaded on your PC.

The TomTom is a bit odd in that it can't see an SD card and internal memory at once. So, you can load the US maps onto an SD card and then pop that out when you're done, or (re)load the UK/European maps AND put the US maps on an SD card and have it all at once. That's the route I took.

Switching maps is convenience itself. You go into Preferences, Switch Map and then Select a Map. That's all it takes... about a 10 second process. The device remembers where you were when you switch maps so when you switch back it'll go right back to the exact location it was displaying when you switched.