2. TAIWAN
Since 1972, the United States has formally accepted the mainland's "one China" formula while maintaining that neither side shall alter the status quo by force. Beijing, however, reserves the right to use force, which allows Washington to justify its continued arms sales to Taiwan. In recent years, Taiwan and China have been improving their relationship. America's decline, however, would increase Taiwan's vulnerability, leaving decision-makers in Taipei more susceptible to direct Chinese pressure and the sheer attraction of an economically successful China. That, at the least, could speed up the timetable for cross-strait reunification, but on unequal terms favoring the mainland.
At stake: Risk of a serious collision with China.
3. SOUTH KOREA
The United States has been the guarantor of South Korea's security since it was attacked in 1950 by North Korea, with Soviet and Chinese collusion. Seoul's remarkable economic takeoff and democratic political system testify to the success of U.S. engagement. Over the years, however, North Korea has staged a number of provocations against South Korea, ranging from assassinations of its cabinet members to the 2010 sinking of the South Korean warship Cheonan. So America's decline would confront South Korea with painful choices: either accept Chinese regional dominance and further reliance on China to rein in the nuclear-armed North, or seek a much stronger, though historically unpopular, relationship with Japan out of shared democratic values and fear of aggression from Pyongyang and Beijing.
At stake: Military and economic security on the Korean Peninsula; a general crisis of confidence in Japan and South Korea regarding the reliability of existing American commitments.
