Method 1; Make a region free backup
You need to decrypt the entire dvd. This will remove the region protection. Then write the decrypted contents on a dvd writable disc. Products like dvdfabhddecrypter can do this.
Method 2; Use a region free dvd player
If your dvd player is region free, it will not care what kind of region your original disc is and will just play.
NTSC versus PAL possible difficulty
But... it will NOT change the American television format (which is NTSC) to the European television format (which is PAL) of the dvd contents.
Luckily 99% of all European dvd players can handle NTSC perfectly.