Again, the main difference (problem) is that the primary goal of the NHS is to provide treatment whereas the goal of the US private insurance industry is to maximize profits for their shareholders by NOT providing treatment.
If you make a claim, it will be fought.
If you are a small business and you have an employee that makes a large claim, your policy will be dropped or your premiums raised to the point where you can't afford it anymore.
The goal is to keep collecting premiums from those who don't use the service and deny or eliminate those policyholders who do use the service.
Bonuses and promotions are handed out to those review doctors that deny the most claims and withhold the most treatments saving the insurance company from so-called "medical losses".

Can you imagine if the police or fire department operated the same way?

The funny thing is that in every country that has adopted Universal Healthcare, "conservatives" fought it tooth and nail all the way up until it became a reality. Afterwards those same "conservatives" changed their tune and would now fight tooth and nail to keep it. LOL