AKC did not want to call them "pit" dogs as dog fighting had become illegal. So they registered them as American Staffordshire Terriers to remove the stigma of the "pit" from the name. Since then, AKC dogs have been bred to a different standard and bred for the show ring, steering them away from the "pit" dog that they came from. So now they are in fact two separate breeds. The APBT
is bred for athleticism and drive and maintains the standard of the original game dogs to the best of the abilities of dogmen today without being able to roll them and test their gameness.
AmStaffs are bred to show and bred to meet the standard set by the AKC. Bred away from dog aggression. So you see, they may share some DNA coding, they are NOT the same dogs anymore.