Yes. Facebook is undoubtedly incorporated in other countries as well. The US could pressure Facebook, but they could move servers elsewhere.
Even if they didn't, the US would have to pressure every single company involved.
More importantly, the US can't just audit bank records from another country. They can't go after Facebook unless they can prove wrongdoing. Offshore accounts protect a lot of bad people for this very reason.
Edit: There also the long term issue. If their currency takes off, the economic power it gives also shields them. Remember too big to fail? We can hardly manage the federal reserve where the government is actually part owner. The situation here would be much worse.
The US just prosecuted Walmart in US courts for stuff their Brazilian HQ did in Brazil.
I'm sure the US could find a way to do the same for Facebook and their investors for how they're using Libra inside the US.
Do you really think a massive US company using some Switzerland corporation is going to protect Facebook and their investors against any regulatory scrutiny?