USA map isn't being found on my Tom Tom one

That is really strange!
I can only suggest that you verify what MAPs are physically on your TomTom device by connecting it to a PC/LAPTOP and use Windows Explorer to look at your GPS drive folders: should see a folder for each 'country' (like GUAM).
The normal way to check which maps are registred and loaded on your device is to use TomTom Home -> Update maps function: it will show you the status or whereabout of any Maps that you have loaded or backup and which one can be purchased.
Hope it helps: let me know how you go.
ps.i f you wisely backup your device on a regular basis (via TomTom Home or direct copy to your PC/LAPTOP), you could always RESTORE FROM BACKUP and start again.

Connect the device to a pc via a usb cable. It will appear as an additional external drive. Navigate the drive and you will fin a folder called Guam.

Copy it to the PC.
There will be another one called USA_and_Canada. check if it has any contents.

The Tom Tom website can tell you how to install the map again if it is not there

http://tomtomproblems.blogspot.com/2009/02/tomtom-guam-problem.html

Reinstall TomTom Home and you should be able to update the maps. TomTom's customer support is also very helpful and can troubleshoot you through the issue- http://us.support.tomtom.com/cgi-bin/tomtom_us.cfg/php/enduser/std_alp.php

connect your unit to your pc when prompted by tom tom press yes. go to manage my one on your home page. on the manage your navigation go to item on device click on maps and check guam box and remove from device. only map left will be usa.

Do you have the back up map of usa? If so you can format the sd card in a card reader from the computer, and reinstall, did your update update tomtom home to version 2? As there are some glitches caused by this update, it may be worth reverting to an older version of TTHome,

This TomTom comes loaded with 2 maps....Guam and the US with Canada. I too got stuck in Guam and it is not obvious how to get out of it. But here it is.
Go to Main Menu, then Change Preferences
Hit forward arrow twice
Go to Manage Maps
Hit forward arrow once and choose Switch Map
It should show you Guam and the US and Canada
Tap US and Canada and it should take you out of Guam!!
Mine did and I am now going to delete the Guam map.

Try clicking on the main part of the screen during navigation. Then click on the "wrench" icon (Change preferences). Then click the blue arrow (2x) until you get to the 3rd page (Preferences 3 of 5). Click on Manage maps. Then click on Switch map. Then select USA & Canada.

Do a hard reset and change to factory seetings in change preferences. This will ask you which map you want. You may also access this through the manage maps feature

Okay, I fixed it and came back to tell the story in case some poor soul finds their way here with the same problem. Some of these tomtoms come with guam as well as us and canada. we didn't fat finger it; for some reason tomtom home stored us and canada on the hard drive (g) and took it off the device when it did its first update.

First, plug your tomtom into the computer and go to "remove items" and remove guam. it will give you the option to store it on the g drive which i did, (in case I should take a notion to go there soon.) this provides more space on your device.

Now go to "add maps, traffic, etc," in tomtom home and scroll the arrow to page forward until you see "items on my computer." click this and then click maps. hopefully us/canada is there, thats where tomtom home had put mine. click "add" for that item and it should upload to your device. this takes a long time. there may be an application that tomtom still wants to update to your device. do this before turning the tomtom off from the computer, i couldn't see that us/canada was there until I did this, and then I had to turn the tom tom off, and bring it back into tomtom home two times before I could see it had the map and was working again.

your compass will also be messed up after you have done any updates at all to your tomtom. this is tom toms new application, there is nothing we can do about it until they fix it someday. the tomtom still works right, you just don't have the cool compass options you had with the original. if you did a back up before you initial update you can go back to the older application if you want.

hope this helps people, as you can see above i was very frustrated because the nice people who really did try to help in this and other discussions had not experienced the problem and did not know the answer. maybe tomtom udates does different things at different times, but this is what it did to mine.