Here, let's destroy a fantasy.
The major military powers of Earth are currently engaged in a thermonuclear standoff. So... which world were you going to start World War 3 with?
Without North Korea and Iran the media would just focus on a different pair of dictatorships. There are plenty to choose from.
Hugo Chavez earned the popular vote under international scrutiny. He is the legitimately-elected leader of Venezuela. You'd usurp him? Why do you hate democracy?
And their infrastructure, and their economies.
So you'd instigate huge destabilizing changes around the world and then quit without finishing anything.
This reasoning is fallacious. The jobs generated by war are low-paying, and conscription (which would be necessary for your world war) displaces prime demographic consumers resulting in deflation. Furthermore, the co-opting of the American industrial base (whatever's left, anyway) to support the military, like in WW2, results in a massive decrease in the production of luxuries and other consumer goods.
The economic recovery before WW2 was a special case. There were indicators that the Great Depression was ending on its own, and due to heavy industry and a vast wealth of resources (neither of which exist anymore) they were able to make gigantic profits off of the Europeans while Americans were still strongly opposed to the war.
Which?
To what end?
The United States Military is the world's single largest consumer of oil. What will be powering your war machine for World War 3?
It's not economical to make most ships nuclear powered when it is possible to build a reactor small enough, and it's impossible to make most ships, any aircraft or any land vehicles nuclear powered. If you're talking about electrically powered military vehicles it's a logistical nightmare, because now you have to somehow make "portable" nuclear reactors (the absolute smallest on the market being the size of a three-story house, and decidedly not portable) and haul them to every battleground, praying to God that nobody accidentally fires an RPG at the retarded thing.
If undeveloped countries have the money to buy oil why are they undeveloped?
The US government already does and always has funded stem cell research. The US government also already does and always has funded fetal stem cell research using existing strains. The only stem cell research that hasn't been funded involved gathering new fetal stem cells, usually because the old strains are losing viability.
Using what money?
So far you've started World War 3. Adjusted for inflation, WW2 cost the United States about $3 trillion. Obviously, however, war costs have inflated a bit since a "small" skirmish over a region the size of California has cost the United States $680 billion. I think I'd be generous if I guessed that WW3 would cost the United States $12 trillion.
You've attacked North Korea, which will increase the cost of electronics enormously. South Korea is an enormous supplier of ICs and the country effectively holds a monopoly on memory chips and TFTs, with most of those manufacturing facilities within the range of North Korea's artillery.
You've attacked Venezuela and deposed their legitimately elected leader. Venezuela accounts for about 11% of American oil imports, and they are the world's #7th ranked exporter of oil.
You've attacked Iran, the #4th ranked exporter of oil.
You've given away American oil to countries that already have enormous debts to developed nations.
You've increased spending on social programs. Currently just Medicare and Social Security account for $42 trillion unfunded liabilities.
You've increased spending on education, which probably won't do anything.