Rationing of healthcare will occur under any system, even in the U.S.
The only difference between NHS rationing -- which, in my opinion, is more like triage than a "death panel" -- and the one in the U.S. is that theirs is based on health status and the American rationing is based on price. It's quite possible that someone not allowed to receive surgery for non-life-threatening procedures in Great Britain would be allowed to receive such a surgery in the U.S. ... but only if they could pay for it.
Frankly, I think it's fairer for non-emergency surgeries to be performed according to health status rather than ability to pay.