I believe the recent No Suprises Act no longer allows balance billing for emergency care or when an out-of-network provider is working at an in-network facility.
https://www.consumerfinance.gov/ask-cfpb/what-is-a-surprise-...
https://www.consumerfinance.gov/ask-cfpb/what-is-a-surprise-...
Got a $2,200 ambulance bill for taking my daughter 6 miles that was balance billed last year after insurance paid $600. Don’t know how land ambulances in particular managed to avoid being covered by the act, but just something to keep in mind if you have a non-critical injury and don’t need an ambulance.
https://www.nytimes.com/2020/12/22/upshot/ground-ambulances-...