Is using VPN illegal in the US?

No, using the VPN is 100% legal in the US for the security purpose and enhancing the user's online privacy and security. However, using the VPN for banned & unauthorized activities is illegal. Using the VPN for hiding the IP and commenting on fraud is still a crime all over the world. There are many other was to in which VPN works. Also read :- https://webavior.com/how-vpn-works/