The Untied States thinks the transforming of Southeast Asia provides both challenges and opportunities to the United States. Under the war of anti-terrorism，the Bush Administration has strengthened the military ties and cooperation with the Southeast Asian countries，extended its engagement with ASEAN through enriching programs such as ASEAN-US enhanced relationship and ASEAN-US Trade and Investment Framework Arrangement，promoted democracy and freedom，expanded public diplomacy in Southeast Asia. Some of its policies have good results，some not. In the future，the United States will continue to strengthen its bilateral relations with Southeast Asia，especially with Indonesia and Vietnam，pay more attention to ASEAN and East Asian regionalism.