Not so much as mandatory duty, its more along the lines of your constructive *right* to act. And even if the state doesn't explicitly have a mandatory duty to act, failure to reasonably act could be seen as criminal negligence. (because even if someone isn't trained at all they must still take the minimum steps that any reasonable person would know to take, such as activating the EMS system, etc.) The flip side is that what is considered "reasonable" under the case law takes into account a persons level of training, and what is available on scene.
Minimally these days CPR equipment should be on scene in most places. I mean there's about ZERO chance someone's getting CPR from me without a BVM being on hand, unless I know this person well enough to trust that their probably NOT a bio threat. This is why I think that every BLS trained individual should be carrying a pocket BVM. They're surprisingly small enough, yet will give full functionality as their standard traditional types. (even though the masks on them suck)
I think you're crossing over into what a lot of us probably think is that it's ethical to help if you can but that's a different topic. I'm purely talking about what's spelled out in law. Certainly not spelled out that we must carry even basic equipment or stop/help at all.