“Buying and selling Bitcoin in the US is still measured and transacted ultimately in US dollars.”
If I buy something using Bitcoin at, say, Egghead, US dollars aren’t involved at all. Just as if I buy a bottle of tequila in Mexico using USD, no pesos are involved.
Easy, eh? A bitcoin (just like a dollar) is worth whatever someone will give you for it.
Sure they are.
USD is our legal currency in the US. Egghead routinely determines that a bitcoin is equal to 'x' USD towards the purchase of a product. They allow the bitcoin to be used as a surrogate - but the bitcoin is not a recognized currency of our nation. The banks would never allow it.
If you want to buy a bitcoin you ultimately use dollars here in the US. If you want to sell a bitcoin then you ultimately get dollars in return.