So after spending $10 trillion on "defense", being able to deter invasions is nothing to scream about. But since the US govt, after spending approximately that amount since 1980, cannot even stop a bunch of flight school flunkies from piloting a commercial airliner into a major, large financial building (i. e. by scrambling fighters in time, by heeding 75+ warnings of the attacks beforehand), there's no nice way to say it: when it comes to defense, it sucks.
What's relevant is the 21st Century world, where, after 9/11, the US spent nearly 10 years and another trillion dollars or so in an unsuccessful attempt to defeat a Third World organization--the Taliban. When any institution, army, etc., after spending a trillion dollars, cannot defeat such a primitive fighting force--one with a 100,000x smaller military budget--it sucks, period.
In the end, it's very simple: people's money should not be wasted on institutions that have a track record of using that money inefficiency. And on that criteria, the US govt is (as described above) second to none.
Sure sounds alot better than Uncle Sam's deal: "if you want us to protect you, you have to pay us $10 billion per month, and then maybe we'll be able to stop a bunch of flight school flunkies or teens with explosives in their underwear."
If a corporation/private entity wants to spend money on something, fine--but it must do it on its own dime, or from voluntary contributions, not by forcibly taking money from me.
I would think a private corporation, funded from private donations, could do a lot better than that.