In the U.S. each state regulates the insurance industry. Hawaii is no exception. While far from perfect, our regulators do a decent job. We also have some aggressive lawyers, with some high profile law firms specializing in insurance claims. The have impressive track records.
When I injured my back my insurance company (my business was incorporated so I had to carry workmens compensation insurance) tried giving me a hard time. I told the claims adjuster she could work with me or deal with my lawyer. No problems after that.
As for medical coverage, I have Medicare and Tricare for life. What Medicare doesn't cover
Tricare pays the balance. Medicare costs me $165/month and I pay nothing for Tricare.
The not-profit private hospital I go to has never asked for a co-payment for the few times I used their emergency room services. I rarely get sick and go to my primary care physician every six months for a checkup. By the way, I am 83 years young.
Sorry about your bad experiences. Take care.