This seems like a sober and accurate analysis, and echoes some of what Mearsheimer observed.  Perhaps the most important observation is that he has actually been consistent over several decades in his thinking about certain issues related to foreign policy.  The author is right that a total withdrawal of the U.S. from the world stage would cause great instability, political and economic, but a partial withdrawal (e.g., stop threatening Russia over Ukraine, stop trying to move NATO to Russia's border) would probably be salutary.