OP here- It's an issue because I have been with this family many years, I have raised all their kids with them from birth. After all these years they don't trust me or have enough respect for me as a human being to tell me I'm being recorded? I live in one of the states where it's illegal to audio record me without my consent, so my rights are also being violated.
Actually your rights are not being violated. Even in states where audio can not be recorded this doesn't extend to prohibiting individual employers from operating home security systems on their own property. If they posted the audio recording on the Internet or published it then they could get in trouble but in the context of home surveillance inside the property this is legal.
How exactly do you know that they never had a camera before this one? Do you regularly search for cameras?
There are many reasons why they may have a cam. Frankly, your over the top reaction gives one the impression that you are exactly the type of nanny who needs some level of supervision or observation. If you have this big an attitude about a nanny cam then you really need to find a new profession.