Defend? Or usually offend other countries?
Aside from Mexico (which was probably itself into defensive mode and had land taken from it) and Japan (re: Pearl Harbor), what credible enemies did the country had that needed defending from in the common sense of the term?
(Armies declaring war and attacking it on its soil/borders).
I don't think the latter deserves much royalty -- especially if it's not fighting defensive wars (in its turf) or expansionists (like Nazi Germany), but wars for "national interests".
Not to mention that the US army never fought the USSR in Eastern Europe. Or that Eastern Europe was more or less divided by the allies with USSR, as if it was their own property -- and that the US occupied the western half of Germany (and Japan).
Left to its own devices, the USSR wouldn't have "eastern Europe" and couldn't afford to get it after the huge WWII cost it paid. But it was given to it, with the western allies pretending to believe BS assurances about Stalin allowing democratic elections there. It was convenient for all sides to get their grubby hands on their side (eastern/western) of the battle-torn Europe.
We also have actual laws about sea routes, and global bodies like the UN that could, if there was an actual need, do something about it.
1. The United Kingdom, and thus Canada, during the War of 1812. 2. Germany in World War I, via the Zimmermann telegram. Although rejected by the Mexican government, the threat was absolutely credible. 3. The Barbary Pirates. Protecting American shipping interests is protecting the country as well, as well as an attack on American territory. 4. Iran during the Iranian hostage crisis. Again, attacks on an embassy/diplomatic mission constitute an attack on sovereignty, especially when those attacks are directed against Americans.
The idea that we fly armed drones over sovereign nations without those country's without a declaration of war against said country is deplorable and I wouldn't want China, Russia, Mexico or other nations to do so over U.S. soil to drop bombs/missiles here. Regardless of the reasons, it's not cool. (strong-armed approval from foreign countries, or permission/payment etc is still not ethical imho)
Not to mention the shear mentality and escalation of cyber warfare, security and domestic spying programs being abused at all levels of govt and shared with private industry. Not just in the US, but a lot of it got worse after US's broad use (stuxnet, etc).
I have nothing but respect for those in the military. I feel that we should absolutely invest in technology that improves or comoditizes usage. That said, the military should be a fraction of what it is, and our spending even more so. I think most government intervention all around should be significantly reduced.
Every time someone in govt tries to come up with a system to do anything, the unintended consequences eventually become worse than the issues they are trying to correct for.