You need the Major Roads map for TomTom in order to travel from one zone to another. Or if you have the entire US as one seamless map, you can navigate from state to state. TomTom also splits the US into zones - each zone encompasses several states. So if you load up the zone that includes IL and TN, you should be able to travel from one state to the other (Midwest region).
http://www.tomtom.com/plus/services/mds.php
If you only have separate states, you will have to navigate from your Home to the state border. Once you cross into the other state, you'll have to load up the map for that state, then navigate to your final Destination. That's why I like iGuidance - you can create maps the way you want - single states, several states, single cities with definable surrounding area by radius.
The GUI for TomTom is nicer, but the maps and voice guidance and map creation for iGuidance are superior.