Earlier quoted context omitted.
Can you explain to a Non-American what forces this system of employer insurance onto the US? Why don't independent insurance companies emerge that offer other models of insurance?
There's both historical and insurance-business (underwriting) reasons. The history: wage-price controls implemented during WWII as labour was taken up by the military and companies had to find some basis other than pay on which to differentiate. Benefits, including health care, were excluded from wage consideration. Insurance itself is the business of assessing, managing, and sharing (or "pooling") risk. In the case…
Adverse selection is the big reason. An individual signing up for insurance can be used as a signal that means "individual is sick" or "individual is likely to need insurance soon". If a company policy covers all employees (or all employees above a certain level), the signal is "person works" which is orthogonal to "person will need insurance" (in fact, it's probably slightly anti-correlated, a.k.a. "person is fit enough to work").