Cost of US university educations: I got my Master's and Ph.D. in a STEM field from one of the world's best research universities and paid $0.00 to the university. And I got free health care. Same for my wife except her field was in the social sciences. Same for my brother. In my department, the word was that they were awash in tuition scholarships and other financial support but were really short on qualified applications.

WWI: My college history course didn't cover that well, and I haven't studied it much since then so can't comment much. But there was something about a prince who got shot and a lot of European countries who had said "if you fight, then we will fight," and somehow soon the rivers of Europe were running red with blood. Somehow the war spread from "Flanders fields" to Russia, destabilized the Tsar, and let the Communist revolution take over. IIRC the US came in near the end, ended a stalemate in the trenches of Belgium or wherever, and walked away. There was the Treaty of Versailles, supposedly really tough on Germany, but I don't know the details. US President Wilson had 14 points or some such, but they never got "traction".

WWII: The US stock market crash of late 1929 ruined the US financial system and threw the US into the Great Depression. Then the US was not buying from industrialized, foreign trading partners, e.g., Germany, and they went into the Great Depression. Germany was already sick from the Treaty of Versailles and the massive inflation they had had in the 1920s. Then, presto, bingo, they got a guy, A. Hitler. He took steps quickly, e.g., used the power he had to improve his position with the citizens, quickly called for another election, got more power, ..., and called for special powers for 4 years to fix the economy. Basically that worked -- he ran a command economy and got Germany out of its Great Depression. Then he called for another 4 years of special powers and, in a word, overreached. His goal appeared to be to get oil from the Mideast, Romania, or in and around Baku. For the Mideast, he had Rommel charging east across North Africa trying to take the Suez Canal (weaken England) and on to the Mideast oil. Then he invaded Russia and tried to get to the Baku oil, came close, but didn't make it. His invasion of Russia was a step too far -- supply lines were too long and the front was too long. Russia was able to fall back to the east since Russia is across 11 time zones. From England, the Allies bombed Germany's war making capacity, invaded at Normandy, and charged east across France. Meanwhile Russia fell back, built tanks and artillery, attacked with 6 million men, won at the big battle of Kursk, and charged west to Berlin. Taking Berlin was to be bloody, and Ike deliberately let Russia do that.

That little description is short, concentrates on the main military points, and omits the nearly worst ever moral record of Hitler's Germany.

The US came out of WWII afraid of, to borrow from a comedy, the Inspector Clouseau "old take over the world ploy", appropriate enough, from the Axis of Germany, Italy, and Japan. Russia came out of WWII determined to have a big "buffer" in the west, to take over the countries of central and eastern Europe, put a big boot on their necks, and make darned sure any instabilities in Europe would not cause Russia to be invaded -- in WWII, supposedly something over 20 million Russians died. Also to keep Russia from moving farther west and to keep Europe stable, the US did a lot to build NATO. NATO has worked -- since the end of WWII has apparently been the longest period of peace in Europe since ..., maybe ancient Rome. The world should thank the US, actually including especially Russia, for what it has contributed to NATO. Russia? NATO made sure Russia would not get invaded again from the west.

Viet Nam: Ho Chi Minh, a dishwasher from Paris, called himself "Communist" and occasionally got a free meal in Peking and Moscow. So, the US, fresh from WWII, saw with Moscow, Peking, and Viet Nam, another case of the Axis of WWII, that is, the "old take over the world ploy" and tried to stop that. The US put in charge their worst and dumbest -- LBJ and McNamara. The US kept supporting leaders in Saigon who, basically, couldn't run the southern half of the country. The US didn't want to level Hanoi and didn't. But Hanoi didn't want a US puppet running Saigon. US voters didn't like the waste of US blood and treasure and voted the US the heck out of Viet Nam. Since then, the US fears of Viet Nam being part of another Axis didn't happen; net, the US is fine with Viet Nam. The blood and treasure lost in that war were awful.

Iraq I: The US had wanted Iran to be one of the states surrounding Russia to keep Russia from expanding, wanted Iran to be a base for surveillance of Russia, etc. So, the US helped the Shah take power. Eventually the Shah was not popular in Iran and got pushed out. Maybe some US business interests wanted the US foreign policy and military to "plow and police" Iran as a source of US business profits -- maybe.

Then Iran was not happy with the US. But there was another war over there -- the 1000 year war between Shiites of Iran and the Sunnis in power in Iraq. So, the US supported Saddam in Iraq. There was the long Iraq-Iran war -- very bloody. Saddam bought enough military equipment from Russia, etc. nearly to bankrupt Iraq. Then Saddam wanted oil prices higher and wanted Kuwait to agree. Kuwait didn't agree, and Saddam invaded Kuwait and was in a position to invade Saudi Arabia. That would give Saddam ballpark 40% of the world's oil, a huge source of power. So, the US and the Saudis agreed that the US should use northern Saudi Arabia as a base of operations and push Saddam out of Kuwait. The US put together a coalition and did just that, quickly. Then George W. Bush didn't like what Saddam was doing and invaded Iraq. The result was loss of lots of blood and treasure, for the US and Iraq. Iraq got thown into a three way civil war, essentially Sunnis, Shiites, and Kurds. Maybe that war is grinding down now, but the whole thing cost the US trillions of dollars (if count net present value).

Afghanistan: That was the base of operations for the attack on the US of 9/11/2001. The US tried to make Afghanistan a better country -- roads, schools, hospitals, democracy, etc. Pakistan wanted some control over Afghanistan and didn't like that US direction. Not enough people in Afghanistan liked that direction. The US lost blood and treasure, maybe $1+ T, in Afghanistan. Now the US is trying to find a way to get out of Afghanistan that won't leave a bloody mess or be a big failure.

Net, what the heck has the US been doing? Broadly the US has been trying to get US and world security with NATO, US foreign policy, military force, etc. The main motivation was WWII and then during the Cold War angry Russia.

In that effort, the US has kept the world out of WWIII but otherwise has fumbled too often, e.g., tried to bring some US style democracy to countries that didn't much understand or want it. Now the US is trying to protect itself closer to home, e.g., mostly at its borders. Now, right away, North Korea and Iran are claiming that they want to use nukes to level the US. Not so good. So, the US again gets involved outside its borders. Apparently for North Korea, the US is putting together a range of pressures and options, including some military options, to stop North Korea from having long range rockets with nukes on top. Apparently North Korea is really angry about something outside North Korea, especially the US; just what they are angry about I don't know. To me, South Korea should be a good example for North Korea: Forget being angry and spending on the military. Instead, just do business and raise standard of living.

But, for the US, South Korea, Japan, and more look to the US as a major source of their security from whatever threats, e.g., North Korea. So, in this way, the US still gets dragged into being a police force for much of the world. Mostly now, the US doesn't want that role.