Former presidential advisor Richard A. Clarke presents this graphic comparing the cyber strength of various nations in his book Cyber War: The Next Threat to National Security and What to Do about It, based on an arbitrary (though well-informed) point system. Higher total scores signify greater potential cyber strength.
The U.S. may arguably possess the world’s greatest offensive cyber capabilities (in terms of dedicated resources), but it lags behind in defense ratings. And in the digital world, defense is everything.
From communication to military operations to energy production, the United States is dependent on cyberspace and information systems for innumerable routine, daily functions--to a far-greater degree than many of the nations with which it competes. Additionally, ownership of the vast majority of U.S. critical infrastructure is held privately among many different firms, rather than being centrally state-owned. This makes standardized, effective defense of such systems more difficult.
The result is what’s known as the Cyber War Gap--the U.S. has both more of cyberspace to defend and a greater dependence on the smooth-functioning of processes within that cyberspace, than nations like North Korea and China. These nations can more easily disconnect from global information networks and continue operating in isolation (with minimal impact on the general populace), due in part because relatively smaller percentages of their populations are connected to the internet in the first place. Put simply, in the cyber realm, the U.S. is essentially on the same footing as, and perhaps even disadvantaged against, the smallest nations, so long as these nations have at least one networked computer.
More information can be found in this article by Colonel Jayson M. Spade, which both discusses the relationship between the U.S. and China with regard to each nation’s cyber security. It also emphasizes the need to focus on cyber defense, rather than cyber offense, in the creation of future national policy.