What I think has happened is that you were looking at a website for this area and the website offered to provide a map. You agreed and it has downloaded this map file to your phone.
All good, no real problem. The issue is that Google Maps on the phone does not have any facility to delete these files.
If you know your way around IOS then you should be able to find this file and delete it via IOS. It will probably have a name related to the area of the map and end with .kml or .kmz
I don't know my way around IOS and so it is probably easier for someone else to help you find and delete the file.
Alternatively, you mentioned that there were other files showing up when you clicked on maps. What you can do is click on one of those other files. When you do that, Google Maps will display that file instead.
Which means that this file will seem to disappear (because Google Maps only displays one file at a time). Of course, it also means that something else will show up BUT being a map it will show up in the geographic area of the map that it occurs.
Depending on what the other files are showing, if you choose one in the USA for example then nothing will bother you while you are in Spain.
Ideally you will have a file that shows something in Outer Mongolia and so it wont ever be a problem