And most US law enforcement uses Glock pistols, which are also famous for having no external safety. There's a lever integrated into the trigger such that the trigger must be pulled before it can travel backward, and there's a safety internal to the slide that ensures the firing pin cannot travel forward until the trigger has been pulled, but there is no external safety anywhere. Pull the trigger (by any means, finger or otherwise -- tangled up in string, caught on a pointy object like a pen, whatever) and it will fire.
I think the new law preventing the suing of manufacturers for not including external safeties is a good thing.
I also think Sig Sauer are intentionally gas-lighting the public on the safety of the P320/M17/M18 and should withdraw it from the market.
Edit: I have nothing against Sig Sauer in general. I've shot a P228; it's a beautiful weapon, and I would buy one in a heartbeat. You couldn't pay me enough to have a P320.