I appreciate all of that guidance, thank you so much everyone! And apologies for the delay. Since you raise similar questions, my response to all three is summarized at the bottom:
What do you want to do? Do you want to work in a hospital, on a medsurg floor/ER/ICU, or in the field answering 911 calls? both are different jobs, with some similarities. You can also aim to do CCT, or critical care interfacility transports, but that's another beast in and of itself.
That is factually incorrect. I know plenty of paramedics who did a bridge course to get their RN and moved to the hospital, as well as plenty of RNs who got their EMT and now play on the ambulance or helicopter.
Depending on what state you are in will determine what you can or cannot do. If you complete RN school, you likely can challenge the paramedic exam, and will have to do a clinical evaluation. If you complete paramedic school, there are some classes that let you bridge to RN.
I will give you my anecdotal experience, and say that the better prehospital RNs (those who function as an ALS provider answering 911 calls) were credentialed medics before going to nursing school.
There are a handful of us on this forum who currently or in the past have worked as both a RN and a paramedic. Most of us were in EMS first and then went on to nursing.
You are correct that outside of critical care transport, very few RNs work in EMS in the US. There are a few states who have RNs functioning in the field essentially as paramedics, but they are very much outliers. For all practical purposes - unless you happen to live in one of those states - you really need to get your paramedic if you want to work in EMS.
The training and credentialing pathways that are available to a RN who wants to become a paramedic depends on the state that you live and work in. Being an EMT-B is always a prerequisite. At one time in New York State, a RN who was also an EMT basically only needed to be endorsed by an EMS medical director as possessing the skills and knowledge required to practice as a paramedic, and was then allowed to sit for the state paramedic exams. South Carolina had a similar process when I first moved there. Both states have since changed their requirements, and I doubt there are many places where it is that easy anymore. But there is probably some sort of shortcut everywhere.
As far as how to do both at the same time, you'll probably have to pick one or the other as your priority job, which for most people will probably be nursing because nursing pays much better than EMS in most areas, and it is generally easy to find nursing positions that offer a lot of scheduling flexibility. Then, find an EMS provider in the area that is willing to let you pick up shifts on the days that you aren't working in the hospital.
The most natural and obvious role for someone who is both a nurse and a paramedic is working in CCT or HEMS. Those jobs are not that hard to come by for a RN who has the requisite experience and credentials, especially if they also have EMS experience. It will take you a few years to gain that requisite experience and credentials, however.
Specific to California: You'll have to find a Paramedic School that will be willing to sponsor you for the Paramedic Internship. You will be required to do both a specific number of "ALS Contacts" and a minimum of 480 hours of internship. Simply having the patient on monitor isn't considered an "ALS Contact." The State EMSA may sponsor/approve of you taking the "written" exam, which will be similar to the NCLEX-RN in how it is designed, but the content will be more specific to EMS. You may be asked to do a Paramedic Refresher course (48 hours) before doing the paramedic exam... and it really would be a good idea as some of the concepts are a bit different from Nursing. That being said, full-up Paramedic School is well over 1,000 hours, it usually takes 1-2 years to complete. Nursing School takes 2 years (4-5 Semesters) to complete, not including prerequisites. If you did Paramedic School first, that's 1 year, during which time you'll be too heavily invested in P-school to do other coursework. Then you'd do about 2 years of prerequisites for nursing school and then 2 years of nursing school. That puts you at about 5-6 years total. If you do it the other way around, that's more like 4 years and a few months for a medic internship. The financial side of it has more of a dent to it... Either way, you're looking at spending whatever RN school costs... but full-up medic school can run north of $10,000. By skipping most of the didactic portion and hospital clinicals, you'll save yourself the vast majority of that cost so RN to Paramedic route will be MUCH cheaper for you.
If you're looking to get into ground CCT, then having about 2 years of solid hospital time (ED/ICU preferred) is good. Having some time as a street paramedic helps in that regard. However, if you're looking for more "high-performance" like flight RN, they'll want you to have several YEARS of ICU time or be an exceptionally good ED RN. Street Medic time helps in that they won't have to train you as much for "scene" calls because that's a whole different game from Interfacility CCT.
Other people on here that do flight RN will be able to give you a MUCH better view into that world but do know that at this point, you're far from doing it. Could I do it? Certainly. My learning curve would be quite steep even given my background and experience.
So, I actually have an extensive background as a career researcher - and more recently I've wanted to become involved in direct patient care as well. I'm at a juncture now where I can continue contributing to research work through consulting/advising, so both the training and subsequent EMS/clinical hours would need to work around my advisory duties at that time. But that won't be a major issue since these appointments will be remote and won't likely take more than 10hrs per week at most.
My personal preference for patient care would primarily be in out-of-facility work - rescuing patients in the field and treating/stabilizing them for transport. Obviously that's the focus of EMS work, the ceiling position of which would be an EMT-P.
However, I would also like to have the option to treat general patients in underserved sites - homeless shelters, rural tribal lands etc. An RN would have a vastly broader scope for generalized treatment options in these settings. There would also be a later option to advance down the NP route for added scope and practice autonomy (depending on the state, CA will be allowing full NP autonomy in 2023) which wouldn't be an option with an EMS background. And of course, as you point out and are well aware, comparative salary between the two fields is also an issue.
In the US system the only qualification short of an emergency physician that would allow for options in both field emergency and homeless/tribal population general care would appear to be in HEMS/flight nursing; I am informed that even MICU for nurses is strictly inter-facility transport, never field rescue. (The exception being as you point out, in specific rural sites where RNs are given field rescue/patient stabilization responsibilities, but in the US these are exceptions rather than the rule.)
But as you correctly state, flight nurse positions are highly competitive and require years of ICU nursing experience at minimum, so this ultimate goal would be a long way off. So during the intervening period, the only option I can see for serving both roles would be as a combined EMT/RN.
Would you all agree, based on your experiences in the field?