I'm sorry about your father.

The Affordable Care Act eliminated the ability of insurers to deny you for pre-existing conditions. (Unlike in Germany, where I have been denied coverage for mine.)

Other than that, there is no such thing as US healthcare outside of the VA. There are 50 different states' healthcare systems, and even in some of those, there's a further urban/rural divide. tldr: Living near a medium-to-larger metro area with a university healthcare system usually grants you the best access, choice of providers, and up-to-date treatments.

I prefer the US system with a non-HMO plan, which is shorthand for "I can pick most any provider because the network is big, and I don't need a referral to see a specialist." I especially prefer the way my chronic illness/disability was treated in the US in a specialty clinic setting, a parallel structure for which simply does not exist in Germany.

I also strongly prefer the digitization of the "US" system. Once I was in a hospital/university system I liked, all my providers there used the same electronic medical record (EMR) system. There was one central online place to communicate with any of them, refer to details I may have forgotten during a visit, request refills, view upcoming appointments. Here in Germany, it's every man for himself, and nobody is for me.

Plus ELI5 - how does employer insurance work if cancer treatment takes someone out of the workforce, and is subsequently laid off?

Germany is superior (federally) in the sense of your care (and/or job) being better protected in the case of ill health or job loss, although some states may have better protections than others (again, that 50-states thing). Yes the bureaucracy, but wait times for decisions on most applications are shorter than similar ones in the US (more on that below).

Not cancer-specific, but: in the US when I was blinded for 10 months due to an MS brain lesion and couldn't see to drive or work, I qualified for FMLA unpaid leave, which protected my job for 3 months. My healthcare was already provided by my spouse's employer plan, which was superior to my options.

But the first communication post-work-leaving that I got from my short- and long-term disability insurance provider was the letter dropping me from coverage because I hadn't paid the monthly premium (which was usually deducted from my paycheck...which I wasn't getting...because I couldn't work).

If you have group/employer health insurance coverage before taking FMLA, you're still covered during FMLA time. After that? You could choose COBRA, which is often prohibitively expensive, but at least it's familiar. If you don't choose COBRA, you have a Special Enrollment Period to apply for a Marketplace Plan, which depending on your situation and where you live, can be really affordable and excellent. There are free advisors who can help you find a plan.

Depending on the severity of the diagnosis and treatment, you could apply for SSDI, which would put you in line for Medicare eligibility after 2 years. Some cancers are on the Compassionate Allowances list (CAL) for faster SSDI application processing (the average wait time is 7 months, and longer in many places even before the current administration's shenanigans), but even with a CAL diagnosis, you have to wait the 2 years for Medicare. The only exceptions are end-stage renal disease and ALS, those can get right on Medicare.

Wherever you live, you'll want to be an informed and proactive participant in your own care, always. In either place, life is better if you can find a primary care doc/Hausarzt who's easy to get in to see and confident in treating a range of conditions well.