We have never had a laissez faire system. The closest we came to it was the years immediately after our founding, where regulations were at a minimum, and they've only increase from there. So yes, due to the regulations and market manipulations of the federal government, we have always operated under a mixed economy, including the '20s.
The only problem was governments failure to function in its proper role, to protect us from force and fraud. Government itself was perpetuating the fraud, through the federal reserve, and using force, by manipulation of the currency and markets, so rather than protecting us from force and fraud, government was actively engaged in, or supporting, fraudulent practices - just as it did in the recent mortgage crisis.
The collapse and banking crisis were results of government intervention. These failures were blamed, as they always are, on "unregulated" capitalism, so the proposed solutions are always more government regulations and interventions... Which create or perpetuate problems, which are again blamed on capitalism, and lead to more government regulations and interventions.
That's a result of abandoning the gold standard not the creation of any government regulatory bodies. When we were on a gold standard, the feds creation of a greater supply of money than was backed by gold created a market bubble and the devastating collapse. Now that our currency is no longer backed by gold, the fed is free to print unlimited quantities of money which still creates market bubbles, still leads to collapse, and just as before, these problems are blamed on "unregulated" Capitalism, but the damaging effects are minimized because of the nature of fiat currency.
The great depression was only "great" here in America, in all other countries its only known as a depression. The greatness of our depression was a direct result of our governments policies which deepened and prolonged the depression.
