That will definitely make them reassess their choices and do the right thing. Hopefully, they will tell their scammer friends to do the same! Problem solved!
I think, honestly, it’s more a bureaucratic nightmare thing. “This wasn’t technically illegal, so we’re not going to comply with your extradition request.” Now it is.
It's a matter of severity and demonstrable willingness to ignore consequences. Scamming and fraud can earn you a spot in prison for a serious length of time, whereas phone spoofing is probably just a fine or probation, IANAL. In general it defies reason that the people who purposely violate existing major laws are going to be dissuaded by tacking regulations onto their methods.
As I recall, certainty of punishment is generally a far more effective deterrent than severity. In any case, what I think the law would really get is leverage against the US-based phone companies who gateway the traffic onto our phone network.
I have a similar dim view of "making something illegal to patch a problem". Though I wonder if there are contract structures that require customer activity to be classifiable as "illegal" for a relationship to be terminated. Given how regulated phone infrastructure is, I wouldn't be surprised if there were laws that "guaranteed access" in the name of forcing the expansion of network access but could be weaponized by adversaries / spammers.
Since the act itself is illegal, blocking cannot be contested.