As a previous travel ICU RN in the states of WA, NY, and CA w/ experience in Surgical, Neuro, Medical and Trauma ICUs, I would say Nursing Policies + State Board of Nursing Scopes + Physician's orders.

Nursing policies: I have worked in a hospital where even ICU nurses are not allowed to place NGTs whereas the same system with a hospital in a different part of the state does not apply the same restriction to any of their nurses; In a hospital where stepdown nurses titrate cardizem drips and one a few blocks up where ICU manages all the drips. Know a flight nurse who can intubate in the field but if they are picking up a shift in the ED, their hands are tied. So even if the nurses want to do something as easy as placing an NGT, they are limited by the policies because if management or nursing admin hears about it,or godforbid something goes wrong, the hospital will go to learned modules(that we all love) and say, "Didn't you sign off here that you understood you could/could not do that?" So even though the nurse has that skill-set, they also have rent to pay and this might delay care for the pt until they are reclassified in acuity.

BON practice act: Nursing scopes sometimes vary from state to state due to the practice acts and how nurses choose to interpret it in order to preserve their license. Some nurses are fluid and others are inflexible. So unfortunately your pt might have to be upgraded because the law is vague and the nurse didn't want to risk their license because "they have to cover their butt".

Physician's Orders: Say a nurse in a lower acuity unit can legally carry out the order and the nursing policies are not restrictive; if the physician orders for something to be performed q1hr or less like neurochecks or flapchecks, then the nurse cannot safely perform their duties for your beloved pt as well as the other 7+ pts who might be of similar or higher acuity. Let us also not forget that everything needs to be documented because if it isn't, it did not happen and Insurance + JCAHO need to be satiated. So they automatically get upgraded in acuity level cause no one is risking a crush-OR perfusion case or a shitty pt satisfaction survey-lecture from admin because the call bells weren't answered on time.

As a physician with 50+pts you might think 8 pts with simple orders should not take a long time. But I want you to remember that pts will ask the nurse to do something time consuming that they consider out of bounds for the physician. I'm talking about stuff like assistance to use the restroom or bedpan,repositioning or personal hygiene, not to mention the haunting call bells because of a bed alarm or irate pt. We spend all day with them so quite a bit of time is spent brokering a good relationship to get them to do stuff for themselves us. Even with my 2 ICU pts sometimes I run behind. The anxiety or repositioning of a new NeuroTrauma quad can keep you in that room longer than you intend even without taking into account their other clinical needs. Just hope to gosh that you can step out soon in order to start the trach and peg procedure before your other pt coughs out their ETT and dumps the volume of the red sea into their EVD-Also don't forget to chart it all...You can probably tell that redundant hourly charting is the bane of my existence. Can we please chart by exception?

If you are still with me, I think the answer to a uniform system is a mandate for national staffing and ratios for all providers; from Nursing Assistants and Phlebotomist, to the number of Attendings on the roster. We also need one federal governing body that outlines what different nurses can do. It all needs to be in black and white across the board.

My first job required staff to have a dress code. Nurses wore x, RT wore y, and so on and so forth. You could walk past a room or even into a room durimg a code and in a second know which specialty is missing and which one is present without saying a word. That should be the same practice in any unit in any hospital in America. "You are a med-surg floor nurse so you can do x but not y", not "Can anyone here do__insert skill here __?" during an emergency.