Seventeen years ago, Thomas Friedman’s The Earth is Flat described globalization and the ever-closer economic and commercial interactions among once-distant nations. Eye-opening as Friedman’s book was, it did not touch on the more frightening security and defense implications of our shrinking world.

Since our nation’s birth, we’ve been blessed with the inherent isolation afforded by “our” oceans, the vast Atlantic and Pacific. For centuries, they protected us from invasion, distanced us from far-off wars, and helped to minimize the “foreign entanglements” that George Washington warned about. Our Revolutionary War victory over the then-mightiest nation on earth was due in no small part to the fact that transit by sailing ship across the Atlantic took months. The British Army’s supply lines were stretched to the limit.

That security blanket has been shrinking ever since. In December 1941, Japan dealt us a stunning blow on our own territory (although still 2,000 miles from the U.S. mainland), attacking the U.S. Navy base at Pearl Harbor. Later in WWII, Nazi U-Boats roamed with impunity off USA’s East Coast, sinking hundreds of ships, some in sight of our shoreline. But even then, the “world war” did not extend to our homeland; we felt the war’s dire impact — more than 400,000 American troops were killed — but we experienced nothing approaching the utter devastation and civilian carnage in Europe and Asia.

Here in the 21st century, the geographical buffer we once enjoyed, thanks to our two giant oceans, is long gone. America’s adversaries today have easier access to the U.S. mainland than ever before — a new reality rammed home two weeks ago by the leisurely coast-to-coast transit by a giant Chinese balloon, and by the several other uninvited airborne guests that followed. This ongoing episode is a reminder of just how vulnerable we are to unwanted intrusion.

A few ominous examples:

• About five thousand active satellites are in the skies right now, many operated by our adversaries, flying over our heads constantly and capable of … who knows?
• New types of hypersonic weaponry — missiles and other projectiles — travel to distant targets at blazing speed. Developing means to detect and defend against them is still a work in progress.
• Thousands of nuclear warheads and delivery systems, infinitely more destructive than the ones that leveled Hiroshima and Nagasaki, are pointed right at us. Because they’ve been around for so long, we’ve tended over time to worry less about them. That’s a big mistake.
• Cyber technology is both our servant and our master. Our appetite is insatiable; we employ it in all aspects of life — financial, communications, transportation, information, etc. — and every time there’s a hiccup in internet or phone coverage, we realize how a massive cyberattack could paralyze our nation.

Political hyperbole aside, the significance of the Chinese balloon episode is inescapable. We know now that it was self-powered (not just drifting along with the air currents), remotely controllable, and carried a substantial equipment payload. We can only surmise its full intelligence gathering capability, but perhaps the most valuable snippet it produced was insight into America’s defense of our air space. No doubt, China wondered how aggressively and how rapidly we would respond. Within minutes? Hours? Days?

The answer, for CCP and everyone else watching, is that we flunked the test. Despite the ever-present threat of adversaries with rapid strike capability, we dithered for a week and then interdicted only after the intruder had completed its mission.

So, is there any good news? Yes. Wakeup calls are always helpful (provided that we actually wake up) and China’s provocation may have been just what we needed. For U.S. citizens and the leaders we choose to protect us, I see several clear and apolitical takeaways:

1.) Forget the notion that warfare is just for history books and action videos. Let’s internalize what we’ve been watching in Ukraine for the past year, the mind-numbing, real-life images of modern warfare on our crowded planet. It can happen anywhere — even here.

2.) Recognize the enormous importance of our borders as the last barrier (here in the U.S., an increasingly nonexistent one) to malicious intruders.

3.) Accept that national defense is the preeminent responsibility of our elected government and recognize as well that the best defense against predators is always superior strength and the demonstrable willingness to use it if need be. That doesn’t mean a wide-open checkbook, but it’s an important counterpoint to the dangerously misguided political view expressed in recent economic debates that entitlement spending is untouchable while defense spending is purely discretionary. We must not drop our guard.

And, of course, we must make it clear to the watching world that our recent, seemingly lackadaisical reaction to the Chinese probe was an aberration. Our airspace is now closed. Don’t go there.