A crackdown would probably be an FBI responsibility, the NSA is not a law enforcement agency and absolutely does not have the authority.
Even if no one goes to jail, the NSA could make residential proxies much harder to operate in the US simply by detecting them and reporting them to ISPs. It would be good for ISPs to then validate the reports properly, give warnings, etc.
- Malware that can record video and audio from infected devices.
- Infrastructure for foreign covert influence campaigns.
- Botnets used in hacking and DoS attacks.