Many people's nightmares are taken up entirely with dark, terrorist fantasies. As understandable as this may be, it's also irrational. Terrorism will continue, but the cost in human lives and economic destruction is relatively small in comparison to more traditional threats to national security. True, Al-Queda or another similarly nasty group could acquire a nuclear, chemical or biological weapon, transport it to our shores and successfully deploy it against Americans, but it's relatively unlikely. Far more probable is the imminent prospect of the US facing a credible threat posed by another nation.
Many people already agree with this point of view but fixate on the wrong countries, particularly North Korea and Iran. The former already uses nuclear weapons as a blackmail prop to secure the foreign aid necessary to buttress its failed economy and Stalinist regime; the latter wants a much bigger saber to rattle over the Persian/Arabian Gulf and Israel. Scary as these two regimes may be, they seem far more obsessed with their own survival than threatening ours.
In truth, only a large, militarily and economically powerful country possesses the capability to threaten us on our own turf. Once, that meant the Soviets; today, it means China. Many people would object to this conclusion, but that's because the focus on the economic similarities to the exclusion of the political differences.
Clearly, the two countries now embrace capitalism with equal gusto. Driven by American consumers, China has achieved unprecedented economic growth. Hence, we owe the Chinese a king's ransom and many many hundreds of millions of Chinese now lead much better lives. Equally, we both rely on precisely the same, non-renewable raw materials - e.g., oil - to keep our literal and figurative motors humming. (Perhaps that's why we share the same willingness to support foul regimes in the Middle East and Africa to gain and maintain secure petroleum supplies.)
Politically, however, there are stark differences. Chinese civil society, never very robust, is being crushed in a spate of show trials, incarcerations and plain, old-fashioned thuggery. Chinese intelligence services commit industrial espionage on staggering scale, block freedom of the press, censor the internet and spy on their citizenry to an extent that would make the Cheney-era NSA salivate. Moreover, it's military has proven willing and able to operate against its own population in Tibet and the Uigher region. And the Communist party (in name only) has proven to be almost entirely undemocratic.
So for all of our similarities and interdependence, China and the US fundamentally diverge politically. Meanwhile, China's foreign interests are growing and ever more likely to come into direct conflict with our own. Theoretically, mutual need should keep everyone sane when this happens, but history's narrative is seldom rational. It's driven by nationalism, pride and self-interest. And when such passions intervene, all bets are off. That's truly scary.