Apparently, while FGM is practiced in the US mostly by immigrant communities (and some health practitioners!), it is also an underground practice in some hard-core fundamentalist Christian sects. Here’s one account I turned up:

https://www.reuters.com/article/us-usa-religion-fgm/u-s-woman-says-strict-christian-parents-subjected-her-to-fgm-idUSKCN1RD2LI