Gotta be careful when talking about "Free Markets".
Thing is, there are generally two different things that people can mean when they say "free market":
1. A "market economy", as contrasted with a "command economy"—ie, more or less the way the US does things, as opposed to the way the Soviet Union did things.
2. An "ideal free market", as described by Adam Smith, which can, in theory, ensure that many systems find a stable, efficient equilibrium that balances consumer desires with producer desires.
The problem is that, however much many (particularly of the Libertarian bent) wish to believe in it, the latter is not real. It is a thought experiment, and it requires a bunch of conditions that don't always apply (eg, perfect information, commoditization, etc). The other problem, of course, is that as I said, the two are often called "free markets" interchangeably without clarification, which leads to much confusion.
You seem to be referring to #1 when you say "there are free markets within the US"; however, what WalterBright is talking about is clearly #2, since he's referring to ways that idealized free markets theoretically operate.