We are were discussing only the U.S. system

You realize you're the one that brought up other countries, right?

However, in the U.S., there is little to no standard best practice, so GPs' choices in how to practice medicine is up to their personal discretion

I love how you make things up with such confidence. American Academy of Family practice guidelines. In which they state:

Chronic rhinosinusitis usually includes the presence of two or more signs or symptoms lasting more than 12 weeks, with or without acute exacerbations. However, the diagnosis requires that documented inflammation accompany the persistent symptoms. Recurrent acute rhinosinusitis, which is a distinct form of rhinosinusitis, is four or more episodes of acute bacterial rhinosinusitis per year.

Chronic and recurrent rhinosinusitis should be differentiated from other causes of illness. Nasal endoscopy and allergy and immunologic testing may be performed, and computed tomography of the paranasal sinuses should be performed when evaluating patients with chronic or recurrent rhinosinusitis.

Same guidelines from the the ENT boards

From the Canadian Asthma and Allergy board

CRS now affects large numbers of patients globally and primary care practitioners are confronted by this disease on a daily basis.

CRS is diagnosed on clinical grounds but must be confirmed with at least 1 objective finding on endoscopy or computed tomography (CT) scan.

Your method still allows for three doctors (or two) prior to getting a diagnosis. All you're doing is replacing an ENT with a radiologist, presumably because you think radiologists are better equipped to diagnosis sinus problems

Again it's obvious you don't understand how things work. Even when an ENT orders a CT scan the radiologist reads it. Everytime. No questions. It has nothing to do with who is better at what.

This patient would have only seen one doctor. No need for ENT when you notice a foreign body that can be retrieved.

GPs should, as a matter of course, assume they are less well equipped than a specialist with issues that fall under the specialty.

You've said a lot of dumb and inaccurate things but this probably the worst. This is actually the problem with the American medical systems. We have too many specialist and not enough GPs. So people get referred instead of treated by their primary. The countries higher in the metric for less money have GPs that do more work.