What backs any “money,” or currency, or economic system is “work.” That is productive human activity and/or creativity.
Which is why so many European economies are in the toilet. Save Germany, Europeans are not acquainted with the concept of “work.” Greece, especially so, and it is reflected in their economy.
And which is why we here in the USA still rule the world when it comes to economic activity.
Most of us still know how to work.
Europe via socialism has destroyed the work incentive and humans respond to incentives.