The backing the US dollar has is the strength of the world's only superpower. It doesn't matter if it's backed by gold or commodities, what matters is whether people believe there's an entity backstopping the currency that can guarantee its stability. That means an entity strong enough to be fully independent, and governed by the rule of law, so that if you're holding a bunch of that currency you can be confident it'll be worth as much tomorrow as it is today.

It doesn't matter if Russia or China peg their currencies to gold reserves, no one trusts them keep the currency market-stable, because they're autocracies. And if Canada pegged its currency to gold or commodities, it wouldn't matter because it's not strong enough to maintain its independence by force, if it came to war.

The EU and the Euro might be a replacement for USD in terms of a currency backed by a big enough, stable enough entity to make it that trustworthy, but that's a long way in the future. Though, as US Treasuries lose their preferred status, European instruments will likely gain from that.