> Apparently USA voters do think the spending is adequate
I'm not sure how well the federal government reflects the will of the people, given how campaigns are funded here, using means which are illegal in most other countries. Not to mention the gerrymandering, where politicians are choosing voters instead of the other way around. I don't know if the federal government was originally meant to be responsive to the people. That's why there's no facility for the people to directly propose amendments or vote on referendums at the federal level, like there is in other more democratic countries. For a long time state legislators elected members of congress and the president, not the people.
You mentioned U.S. voters... Perhaps it is a good idea to have a national referendum before launching a war. Democracy is a good thing, right? I believe other countries would do this, Switzerland for example. Maybe even go one better, and have a GoFundMe to pay for it. And volunteer soldiers to fight. It would then be interesting to see how many people want to waste their money and lives halfway across the world killing people who just want to be left alone, but are in the way of someone over here making more money.