There will be a "cut-out" I'm naming them Steve, between the scam victims and the actual bad guys. So postal investigators can put hours of work in and tie back a bunch of cheques to Steve from Florida, and they go to Steve's house and Steve quickly admits that yeah, he sent the cheques. But Steve is getting paid $100 per week to send dozens of cheques, and Steve is
so dumb his only contact "up the chain" is to somebody named "Bx$cash$$" on Telegram who told Steve it's a legitimate business venture. Steve is completely sure Bx$cash$$ is a 20-something woman from Utah, but the investigators aren't morons unlike Steve so they guess immediately that's a stock photo, and Bx$cash$$ has almost certainly never set foot on any soil with extradition to the US. Dead end.
Could they charge Steve with crimes? Yeah, and I guess if they're frustrated or Steve was obnoxious and unco-operative they will. But he's a dead end, there is no route to Bx$cash$$ whoever that might be, through Steve, and so long as America is a land of morons who dream of being billionaires there will be more Steves so why even bother?