Check out this excellent article.
The United States has the world’s largest economy (so far), and the world’s most powerful conventional military forces. It spends about as much on national security than the rest of the world combined, and nearly nine times more than the No. 2 power (China). It has several thousand operational nuclear weapons, each substantially more powerful than the bombs that destroyed Hiroshima and Nagasaki in 1945. America is further protected from conventional military attack by two enormous oceanic moats, there no great powers in the Western hemisphere, and it hasn’t been invaded since the War of 1812. (A few southerners may want to challenge that last statement, but I’m not going to get into that).
9/11 reminded us American security is not absolute, of course, and the strategic advantages I just outlined are no defense against climate change, pandemic disease, or financial collapse. But surely the United States is about as secure as any great power in modern history. Yet Americans continue to fret about national security, continue to spend far more on national security than any other country does, and continue to believe that our way of life will be imperiled if we do not confront an array of much weaker foes on virtually every continent.
One reason Americans exaggerate security fears is the existence of an extensive cottage industry of professional threatmongers, who deploy a well-honed array of arguments to convince us that we are in fact in grave danger. (The United States is hardly the only country that does this, of course, but the phenomenon is more evident here because its overall strategic position is so favorable). Debunking these claims is easier once you know the basics, so I hereby offer as a public service: