The Obama,Trump and Biden administrations all face a similar strategic challenge,i.e.,in the midst of power transition,how to sustain U.S.dominant influence in multiple regions(Europe,the Middle East and the Indo-Pacific)?The Biden administration has made efforts along three lines:completing the total withdrawal from Afghanistan while trying to maintain the U.S.credibility;safeguarding the U.S.interests in the conflicts in Europe and the Middle East while trying to avoid escalation;pushing for collaboration between U.S.allies in Europe and the Indo-Pacific.These efforts have paid off to a limited certain extent,but they have not solved the more fundamental problem of the mismatch between resources and objectives.