Is KYC mandatory in the US?

I'm curious to know if KYC, or Know Your Customer, is a mandatory requirement in the United States for cryptocurrency transactions and financial services. With the increasing popularity of digital currencies and the rise of decentralized finance, it's essential to understand the regulations surrounding customer identification and verification. Can you provide some insight into whether KYC is a legal obligation in the US, and if so, what specific laws or regulations enforce this practice?