The U.S. engineer can be fired on a whim immediately and lose their health care (COBRA) and the company that fires them can even contest their unemployment benefits (that the employee paid into) if they feel motivated enough. That's one of the reasons they get paid much more.
I’ve been fired before by a major American tech company. I was underperforming, unmotivated, and depressed about it. They gave me a substantial severance payment in exchange for quitting voluntarily, and for signing an agreement that basically said I wouldn’t sue them. They let me pick my last date, they paid my health insurance through the next three months, and my manager told me I could use my last month of employment to find a new job. I was quickly hired into a better-paid position at another company, with a better manager, and I did well there.
I realize this story sounds absurd to anyone who hasn’t experienced it, but my understanding is that this form of firing (“managing out”) is basically the norm for low performers at top-tier tech companies.
To get actually fired, you usually have to fuck up big time, like sexually harassing a coworker, stealing trade secrets, or trying to start a union. (That last one is a joke, sort of)