Callers are located in India and Pakistan and they ignore all US laws. There's nothing the US can do and the local governments do little.
Invest in a call blocker and DO NOT pick up on call numbers you do not recognize. Common scam, been around for years.
Received automated voicemail saying to contact before legal action would be taken, called number and a bored voice picked up and said "IRS, how can I help you?" with a lot of noise in the background. I hung up. IRS doesn't answer phones like that.