Moreover, for all our missteps at various levels of government and the public-health bureaucracies, the U.S. developed vaccines and treatments with stunning rapidity. As a medical issue, now-endemic Covid is a lingering challenge, particularly as new strains diminish vaccine efficacy. But the virus was never an existential threat. Like climate, another real but hard-to-quantify challenge best addressed by technology and ingenuity, Covid was regarded as an existential crisis only by irrational people, very much including political leaders, who’ve lacked actual existential crises to fret over.

We no longer have that luxury.

China has emerged over the past 30 years as a hostile and formidable rival, angling to supplant us as the dominant world power. To be sure, it has profound internal problems. Years of prosperity and miraculous growth were never going to hide the monstrosities of communism forever. Plus, China’s economy has markedly slowed, while its aggression, corruption, repression, and lack of reliable legal and market institutions ensure that harder times are ahead as its population ages and plummets. We should take little comfort in this, though.

As demonstrated by Putin’s Russia, which remains a geopolitical rival but not nearly of China’s dimension, periods of internal strife and decline tend to be when authoritarian aggressors are at their most perilous. After Russia gobbled Crimea with virtual impunity, there was nary a peep when China took Hong Kong. The greatest ambition of the new Mao, Xi Jinping, is to take Taiwan. While we tell ourselves he won’t really do it, or that the possibility of an invasion is five or more years away, the truth is: It could happen at any time. Our commitment to defend Taiwan is uncertain: If we mass allies and go to war over it, it is by no means clear that we, from 8,000 miles away, would win in militarized China’s backyard; on the other hand, if we fail to defend Taiwan, then the world will have become a much more dangerous place,and our place in it would be in grave doubt.