Your last paragraph suggests your understanding of US healthcare is entirely theoretical. In practice, COBRA is frequently so much more expensive that it wouldn't be affordable even if you hadn't just lost your job. In practice, millions of people are trapped in jobs they don't want but can't leave because they need healthcare and will lose access to healthcare if they lose the job. It's a stupendously shitty system that gives US employers even more of an upper hand than they would otherwise have.