The North_America_2gb should be the name of the folder for the map and it can reside on either the sdhc card OR internal BUT there should not be files with the same North_America residing in both places UNLESS you have, for some reason, a North_America map installed in both locations.
Use Explorer and look in the NA map folder on the sdhc card for a file with the extension . of .pna. It's a text file and one row in there shows the map version number.
If you also have a NA map on internal, do the same.
Also, use Home's Manage my Device, device tab, map and see what it says.
Then switch to computer tab, map and see what it isays.