there are metallic fibers of a certain length embedded in the paper.
If you have a strong RF signal, and look at the return reflection, you can estimate the amount of money. However, this takes a very strong transmitter, and a very controlled environment — think of an x-ray scanner at the airport.
So although it’s possible on a local basis, the idea we can do that from space is a bit far-fetched, as it would take dedicated very high power satellites (which we may have but I doubt it).
No, the strip in US money is not metallic. It is polyester.