What states ban add-on GPS units?
And why would they even do that?
The fact is that if a built-in GPS breaks down, it is going to cost bigtime to fix it, and you will probably only be able to get it fixed at the dealer.
It will be obsolete within five years.
If you buy an add-on device, you can simply REPLACE it with a more modern unit for a fraction of the price of fixing the built-in unit.
Not long ago, GM discontinued their old OnStar and replaced it with a newer version., Those who paid extra for this were screwed.