For the last section, you're ignoring the fact that inflation always happens in a growing, active economy (the US dollar was still backed by gold in 1913, as it was up until around the 70's I think, and inflation still happened), and with a country with such a massive economy as the US, it's impossible to have a commodity-based currency. There's literally not enough gold in the world (unless you stockpiled every last bit of it) and silver... eh. Maybe silver would work.
I think the main issue with money now is that more and more of it is becoming digitized. We're not talking about fiat money; that's what the dollar is. It's a physical thing with no intrinsic worth that we put value on because other people value it. Digital money is even more of an illusion than fiat money. But with globalization, how else are we going to ship funds around? Coins are heavy and take up a lot of space, plus it would take a long time to ship money to the other side of the world. I'd think most countries would prefer digital currency if only for the ease of transference.