On the topic of macroeconomic history, I can provide some insight. The majority of initiatives, including the CCC (Civilian Conservation Corps), WPA (Work Projects Administration), and comparable ones, had a relatively tiny but net-positive direct economic benefit. You may argue that teaching someone a trade has spillover or multiplier effects, but I'm not aware of any such work from that era. For instance, the New Deal included a minor amount of expanded utility regulation. This resulted in regulations like the requirement to electrify rural regions. Although it is difficult to quantify the exact economic effect, it is clear that rural America was now more accessible for continued economic growth. Generally speaking, across all types of government investment, infrastructure improvement has one of the highest multiplier rates (food stamps, which is an FDA program, is generally found to have the highest).
The establishment of Social Security was the primary change. Before its inception, many low-wage employees retired in growing amounts of poverty (read: no longer able to work). Elderly people living on the streets were very prevalent. Meaning that, for the majority of individuals, this was their lot if they had no relatives who could care for them. Social Security has made this circumstance so rare that it no longer occurs. Widows, widowers, children with deceased parents, etc. are also covered by Social Security. These were people who, if they suffered a workplace injury or their husband passed away, would have been in a very precarious situation even just a century ago. Therefore, it is acknowledged, at least in macroeconomics, to have lessened some very serious social issues.
The New Deal included regulations for many industries. In particular, telecommunications (the FCC was founded in 1934, how pertinent) and pharmaceuticals A moratorium on farm foreclosures was also in place. I'm not sure if this has had a positive or negative impact.
Now onto the next part of this.
Without a doubt, World War II revived the American economy. The tremendous government expenditure during World War II and the New Deal, however, are unconnected. It is a characteristic of macroeconomics that large-scale government expenditure is significant in this circumstance. My spending is your income and vice versa in the bigger economy. Only the government is left to make up the shortfall in spending if the general public lacks money to spend and businesses lack motivation to spend because they have few customers. Since my income is derived from your spending, the economy will not perform to its full potential if the government decides not to spend.
However, what about the debt that is incurred? After the war, the US government had enormous debt commitments, but the economy was thriving as people spent after years of restrictions that had stifled demand. As a result, the debt mostly disappeared. Say the government's debt is 100% of GDP to help understand. Rapid economic expansion lowers the debt as a proportion of GDP. The debt burden is further reduced when a healthy amount of inflation is added on top of this and occurs in tandem with business cycle upswings (Krugman discusses this subject frequently; he is not the best source, but if you look around, you can find many other articles with excellent data).
Macroeconomic historians and economists may learn a great deal from wars, their debts, and the taxes they cause. This is best shown by the American Civil War. The government had to enact a tax because there wasn't an income tax at the time; nevertheless, once the war debt was settled, it eliminated the tax. I believe it took seven years to repay. In actuality, the English's use of bonds to fund their war against the French is largely responsible for the development of modern finance. Many of the payoffs were never claimed because the payoff dates were set past the life expectancy at the time. A brand-new class of super wealthy people emerged in Britain as a result of some of those who did receive their payouts.
Thanks,
Eddie