One example, that shocked me, was that it cost the US military just shy of $4mln to keep an American solider in Afghanistan for a year. Here's the info from TIME: "the CRS report says the cost of keeping a single American soldier there this year is an eye-watering $3.9 million." We are spending huge sums. And now...
I hate "facts" like these. They have a kernel of truth, but lack context and are designed to get people riled up one way or another. As I understand this particular metric, you take the total amount the military spends in one area and divide by the total number of combat soldiers and ... voila, $4MM/soldier. It's both shocking and not particularly helpful. It ignores all the infrastructure, contractors, and military support (lots of aircraft), and it doesn't scale particularly well - i.e. if you double the number of combat soldiers you don't double the cost (because much of the 'support' is already there).
Yes, we are spending an almost ludicrous sum on our armed forces during a time when our country is, historically speaking, pretty safe from external threats. We spend more than any other coutnry, and more than the next 8 countries combined (most of which are our allies).
So irrespective of party in power we are going to pour more money info a country that we totally messed up in the 1980s, when we could have done things at least a little better.
To be fair the soviets kinda leveled Afghanistan - we just supported the counter-insurgency. Part of the "American DNA" seems to be a steadfast belief that the world can be a better place, and we ought to be the ones actively making that change. It's not a bad instinct and much good has come from it, but it also gets us into military quagmires when we think that our intervention will suddenly create new strong democracies.
...and now Trump is so convinced of his own brilliance that he thinks he will usher in peace in the middle east after several millenia of ethnic wars. That's literally been the belief of the last 8+ administrations.