An FNP can work anywhere that is within their state's scope of practice law (with caveat below). So, by that, the question to you would be, what does your state's scope of practice law say in regards to this?
The caveat to this is: does your local hospital, or the hospitals within your region, hire FNPs? If so to do what role? Within the scope that your state allows, facilities can choose whomever they wish to hire. Either by having formal limitations, or informal ones. They often consider insurance reimbursement limitations in your state in making these decisions.
My own state's SOP law is very vague on this, basically saying that if you are trained to perform the work, you can do it. Thus there are ERs in my state that are fully staffed by NPs. I'm only partially familiar with them, so I can't say how they determine if the provider is trained to treat all of the patient population that is/will come into the ED. I also know of several EDs in other states that are staffed by NPs exclusively. All of these hospitals that I know of are rural hospitals, and at the very least the vast majority of the NPs are trained as FNPs (I don't have the credentials of all the providers here).
My own local community hospital has two providers, one MD 24x7 and one NP/PA 12x7. The mix of NP to PA has varied over the years. All of the NPs are FNPs as the facility wants them to be able to see all patients. One ACNP was considered mainly because she had many years of experience in our ED.
Officially, our ED policy states that the NP/PA take levels 3-5 pt only unless the physician is overloaded and directs them to take 1&2s. Unofficially almost all the providers split the patients on a provider available basis. Level 1&2 probably get a physician 75-80% of the time. Also, our provider group has protocols for the providers to become checked off on skills (for physician provider as well as NP/PA, many of the physician providers are not board certified although they are working on improving that ratio), so that is how the group and facility meet the "trained" aspect of the SOP.
My own facility has toyed with the idea of, and hired both NPs & PAs for the hospitalist group, but they have never stuck. I think the main issue has been the distribution of work, basically the physicians have only given the grunt work to the NP/PA. In the cases I know of the NP has been an FNP, again for the reason of all age groups. I think this will improve over time, and at some point there will be FNPs hired into the group that will stick. I know of several FNP Hospitalists in many states, so I have to believe we will figure out how to make it work at some point.
The medical director of our ICU has expressed interest in hiring FNPs to staff the ICU. At this point it is a proposal, so I don't know where that will end up. Again there will be issues of putting the proper training and checkoff procedures in place to meet the SOP.
Personally, if I was to try to make a career in any of these settings, I would consider going back and getting my ACNP.