I did some additional research and apparently in some states if you are present and appear to the public to be a rescuer on duty, you will have a legal responsibility to render aid. So EMT plates or being in uniform might be enough for the public to believe you are on duty as an EMS personnel and therefore are legally required to assist. However, an RN license plate is less clearly a duty to assist because an RN is not an emergency responder. Scrubs certainly do not equate to a legal responsibility but a visible hospital badge might-again in certain states and more for EMS personnel (firefighters, police, EMTs).
Duty-to-rescue laws: Legislation that requires certain people-those who perform rescues as part of their job-to rescue people in need. These people include firefighters, police officers, and emergency medical technicians. Only a few states apply duty-to-rescue laws to nurses.
From Nurse's Legal Handbook by Stacey A. Follin page 381
One source stated that there are eight states that have duty-to-rescue laws requiring people to assist at accident scenes: Florida, Massachusetts, Minnesota, Ohio, Rhode Island, Vermont, Washington, and Wisconsin. (from Wikipedia, which I don't consider an absolute source due to lack of complete source citing). Another source, from the Texas Law Review, I do consider accurate and this stated there are 3 states with these laws, but didn't list the states, except for Vermont. However, this source was older so perhaps in the interim, these additional states have adopted such laws.