Which card you show has absolutely no bearing on liability ... any lawyer worth the name will discover everything they need to know about you, including your current certification level.
First off, let's start out by saying that in the USA, anybody can be sued for any reason (or none at all) at any time. We live in a society where (a) there is no penalty for frivolous lawsuits ... and therefore no incentive not to create one ... and (b) people are culturally predisposed to an "it's not my fault" mentality ... even when they do the stupidest things. So let's separate the concept of "you can be sued" from "you can be found liable" ... they are not the same thing.
In order to be found liable, the plaintiff must prove the following ...
1. You had a duty of care.
2. You failed to fulfill that duty
3. The circumstances that led to that failure were foreseeable
4. The failure of duty caused or contributed to an injury
Without establishing those four things, there is no liability.
So let's look first at duty of care. As a certified Rescue diver, you have no inherent duty of care to help anybody. You can establish a duty of care by deciding to take action to help someone ... and once you've established that duty, you MUST fulfill it to the level of your training ... and within the limits of your training.
You can fail that duty either by trying something you were not trained to do, or by not following the procedures you were trained for. This is where it can get tricky ... because the reality is that every accident has circumstances that are going to force you to make decisions ... often snap decisions ... and those can, and will, be questioned by plaintiff's attorney. Your actions will be judged based on the question "what would a reasonably prudent person do? If you have acted within your training and ability, then you have met that standard, and have not failed in your duty of care.
If it's determined that you did make a decision or take an action that did not meet the standard, then the question of foreseeable comes into play. Did you know, or should you have known, that your actions would bring harm to the plaintiff?
And finally, unless it can be demonstrated that something you did either caused or contributed to the plaintiff's injuries, you are not liable.
In most states, Good Samaritan laws protect rescue divers ... because it is recognized that unselfishly attempting to help someone in distres is an activity for which a person should suffer no harm.
So the short answer to your question is that no ... getting a rescue certification does not increase your liability in any way ... as long as you act in good faith and do not attempt something you weren't trained for ...
... Bob (Grateful Diver)
