Realistically, could millions of average Americans afford to put enough cash into 'Health Savings Acc'ts' to really make a difference?

Most Americans probably could not put away enough. Many Americans are living essentially paycheck to paycheck and can't save any money. Others could only save pocket change and they're already supposed to save for other things like retirement. The other thing is that health care is so expensive that even fairly minor things could wipe out a large chunk of someone's savings. If you had a major condition like AIDS or cancer or something then that would be even worse. That's why we have insurance in the first place, because most people can't afford to pay for anything but routine health care on their own.

Define "enough cash" and please put context to what "difference" it is supposed to "make".

The whole point of HSAs is to allow people to save, tax free, money that will be spent on paying deductibles and other medical expenses until they reach their cap and the insurance starts paying for most/all of it.

McCain's plan was to expand HSAs so individual plans would have them, as well as give medical tax credits to people to help pay for insurance and deductibles. It also featured portability as well as more competition and free-market policies that would have made it more like car insurance, but even better than that. Please note that ObamaCare rejected these because it is inherently aimed against individual plans.

There are many ways to make health insurance affordable for people; ObamaCare is probably the worst way to do that.

Very doubtful. Many people seem to live pay check to pay check. I can't see millions of people (particularly those near the economic bottom) saving enough money for medical needs to take care of things.

Nope. But it will put a load of money in accounts that will make wealthy republicans even wealthier. Some day, their constituents will realize that the sole function of the republican party is to make rich people more rich.

Absolutely NOT happening

Realistically, no. Not the remnants of the middle class (or those who used to be).