Just a side note: The product may not already be "in the wild". Only one squid in package showed contamination, and the source of the contamination is unknown. It's possible that it was contaminated in plant handling by a human. So without more info, they can't know if a ban is even needed.
The reason that finding this type of contamination in food is such a concern is that it hasn't been found there previously. Normally, antibiotic-resistant bacteria come from infected people and places where they are cared for, so it coming from a human (not the ocean) makes the most sense.
The CDC report made this suggestion, "Finding a carbapenemase-producing organism in food in North America creates an urgent need to expand tracking and monitoring (surveillance) of these organisms." It also acknowledged that because South Korea was probably the source of the squid, that location should now be considered more of a hazard for travel for anyone who is immuno-compromized.