In support of U.S. alliances (Richard C. Bush, Brookings)

United States alliances with East Asian countries are not a fight-for-cash proposition, as Donald Trump continues to suggest. They are an important instrument of U.S. national security strategy, whereby we have chosen to defend the homeland by forward deployment of our armed forces in the Asia-Pacific. Moreover, our allies pay a significant cost of our presence (around 50 percent in the case of Japan and Korea) and bear the primary responsibility for defending themselves. To suggest that the United States would help their defense only if “the price is right” only fosters doubt in the minds of our friends in the credibility of our commitment.

https://www.brookings.edu/research/in-support-of-u-s-alliances/