I hope there are even more of them now. It would be pretty cool to read about a contingency plan for an insurgency against a Klingon or Cylon occupation of the earth. That would be an interesting scenario.

Think about it, would it be better for the US military (not to mention the world) to spend it's money on training simulations to improve officer quality, or actual drones and bombs being used in actual wars? Scenario 1, IMHO, is much better for humanity.

There are likely more now than there were in the 1930s. The US officer corps has expanded greatly since then, and computers and better information likely makes creating war plans much easier. Planning a campaign is much easier when you have a database containing a topographical map of the entire planet and the suspected arsenal and troop distributions of every nation, instead of having to dig deep through archives for the right atlas and hoping a military mapmaker has happened across that beach before. Fun fact: the Allied forces lacked military maps of the beaches of Northern France, so had to enlist civilians to send them copies of any vacation photos they happened to take there, and tried to re-assemble them to figure out which beaches they could land at.

EDIT: In terms of war plans the pentagon most likely has, there's the obvious war plans against North Korea, Russia, China, and Iran. I'd expect there to be several variations of each of those: like one for rebuffing a Chinese invasion of Taiwan, another for a naval conflict in the South China sea, the North Korean war plans probably have different variants depending on whether or not China supports North Korea, etc. Probably some for interventions in various world hot spots: Syria, Libya, Ukraine, Somalia, Venezuela, Yemen, Sudan, the DRC, maybe the Gaza strip. And those plans would likely also have several variations based on the scale, from a couple special forces operations and an airstrike to a few peacekeeping troops to a full invasion involving multiple carrier groups and multiple divisions. In terms of far-fetched ones, I'd expect at least one preparing involving the breakup of NATO, like two NATO members going to war. One case where it's a NATO member attacking the US, another where two other NATO states go to war and the US tries to negotiate a peace, and maybe one where it's an all out civil war where each NATO member picks a side. Invasion plans for any of the US allies where the relationship is complicated or strained: Saudi Arabia, Bahrain, and Turkey off the top of my head. Oh, and invasion plans for anywhere that control major sea lanes: Indonesia, Malaysia, Singapore, the Philippines, Panama, Egypt

Every new generation of officers to come out of the military colleges writes a few new ones. Nobody is born being good at planning, you have to practice.

The Pentagon had a plan for the invasion of Iraq that was loosely followed. The State department did not however, leasing to the mess predicted by the Pentagon's plan. Additionally, limited information is available about several North Korea plans.

Canada and Mexico may still have some plans, but the US's primary strategy is just to ensure an anti-US regime can never get power. So more the CIA's area.

No, in fact there is reason to believe there's more of them.