Depends on where map of Europe is.
I was talking about the card. If the map is in internal memory of device, let it there, don't touch it.
You have a dedicated device and if you broke something in it, I don't know how you can repair.
I don't know much about Garmin devices, but as far as I know, in the memory you can have gmapprom.img(Europe), and on the card you can have another gmapprom.img and gmapsupp.img. So, be very carrefull when you transfer maps in device.
So, on the card, try to have Romania as gmapprom.img and Bulgaria as gmapsupp.img. If the software doesn't see one of these countries, maybe you have to create the .unl file. You know, with Garmin_KeyGen from JetMouse with the MapID.
Or, you have to merge Romania and Bulgaria in one file, gmapprom or gmapsupp depends on how Garmin see it.

I hope that I didn't confused you.