[thephyber]

> because $1 = $1 like forever

No. $1 during the gold standard was different than $1 after we left it. Now, our central bank (the "Federal Reserve") aims to inflate our currency at +2%, every year. After 80 years (roughly a US lifetime), $1 at birth is worth $0.20 at death. And central banks can't always keep monetary policy under control.[1]

We just hit $20 trillion in US federal debt. It's set to continue to grow as baby boomers continue retiring. Congress has no spine to make large cuts in spending (for defense, discretionary, or entitlement programs). There are a handful of very large states in the same condition. The debt will continue to grow reasonably fast while the GDP of our economy has lagged.

$1 USD may say "$1" on the front forever, but the purchasing power of a dollar isn't likely to stay as strong as some other currencies. It's worth even less if large, important international transactions (like for oil/gas/weapons) are done less and less with the US dollar (@see "Bretton Woods" and "petrodollar").

[1] https://en.wikipedia.org/wiki/Hyperinflation