Where is the wait only 30 minutes? Every time I've been to the emergency room the wait has been 6+ hours. I think the only way it would be that fast at the hospitals I've been to is if you'd die waiting longer, otherwise it's a long wait.
"Wait" can be defined very differently. Wait time to get triaged by a nurse? An ECG for chest pains? Initial physician assessment? Entry-to-exit? Lab results? Time to X-Ray if needed?
Lots of directives may be in place too. In an efficient system, the nurse is empowered to "order" many procedures that screen out serious things that require immediate physician intervention. Or just to save time like ordering an X-Ray first instead of waiting to see a doctor to order it and then waiting again for it to come back to review.
I've waited less than an hour in New Jersey and Connecticut.
When I still lived in NYC, I resolved that if I needed a hospital but I wasn't in extremely bad shape, I would drive an hour into an adjacent state's ER rather than wait in NYC.
Coming in via an ambulance doesn't trigger some sort of re-prioritzation, if you're not suffering from something that is immediately life threatening.
In most NYC hospitals, you will end up in a secondary waiting area that lies just beyond the regular ER doors.
Good luck if it's a Saturday night.
https://projects.propublica.org/emergency/
Where I live, all in driving distance have an average wait time more than 2.5 hours.