I live in Europe and use my TomTom often when we take a driving vacation. I use the TomTom MyDrive program set up on my laptop to coordinate our trip, add "must see's," hotels, and even lay out the day-to-day route. The ability to do all this on a computer and then download the info to your GPS is great and makes trip planning far easier. Our TomTom does have both USA and European maps.
Granted, because we have Dutch phones with unlimited data in-county (and 21 GB per month in other EU countries), I do prefer my phone when walking in-town (a lot easier to carry around!). I suppose it depends on how detailed you want to be in trip planning and optimizing the usage of your TomTom.