Randy Schweller is a highly respected realist analyst, but he illustrates that realism has many variants. He cites a nationalist Republican realist tradition dating back to Lodge and Coolidge, but there is another Republican tradition exemplified by Eisenhower and George H.W. Bush who also considered themselves realists. For all the flaws in American foreign policy that he cites, I would argue that these post-war realists did far better than their pre-war predecessors who bequeathed to us a 1930s of depression, genocide and world war.
As I argue in Do Morals Matter? Presidents and Foreign Policy from FDR to Trump, one should start with realism, but too many self-styled realists stop where they start. The issue is not "America First" or defense of the national interest, but how that interest is defined. Eisenhower and Bush 41 defined it broadly in ways that incorporated others. Trump defines it in narrow transactional terms that exclude others. Indeed, as one reads the first hand account of John Bolton (another flavor of Republican realist), Trump's definition of the national interest often had more to do with his narcissism than with realism.
While fair-minded critics can legitimately differ about the breadth and attractiveness of the values Trump expresses, an impartial analyst can not excuse the ways in which his personal emotional needs skewed their implementation. Trump’s need for personal validation and proclaimed success led to flawed policy that weakened American alliances—for example, after his summit meetings with Putin and Kim in 2018. Declaring the nuclear problem in Korea solved and stating that he believed Putin more than his own intelligence chiefs was not good realist policy or management.
As for prudence in balancing values and risks, Trump’s noninterventionism protected him from some sins of commission, but one can question whether his mental maps and contextual intelligence are adequate to understand the risks that the United States faces in the diffusion of power in this century such as pandemics or climate change. Unwillingness to confront unwelcome evidence is culpable negligence. Withdrawal from the Paris climate accords or the World Health Organization is not a sign of realism.
To his credit, Trump’s uses of force against ISIS or in response to Syria’s use of chemical weapons were proportional and discriminate, and he cited proportionality as a grounds for cancelling a military reprisal after Iran shot down an American drone. He also deserves credit for pushing back on abusive trade practices by China, but it would have been better if we worked with our allies to isolate China. His phase 1 trade deal has been costly for Americans but has not changed the trade imbalance and merely postponed the more important technological issues.
Historians remind us that a proper assessment of the consequences of Trump's foreign policy will require more time to pass, but as an interim assessment, I would say that the U.S. benefited more from the liberal realism of Eisenhower and Bush 41 than it has from Trump's amoral narcissistic realism.