There are some mitigating factors. The primary purpose of a border closure is to prevent, or at least control, the introduction of the virus into the country, especially to let the health services prepare better. Viewed from this context, Trump's border closures look especially asinine:
* The closure (at least with respect to Europe) occurred by which time it was widely known that the US had uncontrolled community spread.
* The closure applied only to non-Americans, which made it a really, really porous closure. New Zealand's closure applied both to Kiwis and non-Kiwis.
* The administration of the closure was also chaotic and inept. There was no real effort to screen for COVID-19 among the many people who were let in during the closure, and the fact that the arrival halls were jam-packed with people only exacerbated any potential spread that might have happened.
* Similarly, there was no real effort to use the time afforded by the closure (even had it been more effective) to improve testing and tracing infrastructure.
* The actual announcement of the rollout was extremely botched--the White House had to issue three separate statements afterwards correcting Trump's announcement.
* Finally, it's been pretty clear in the months since then that Trump believes that being proactive in the (ineffective) closure efforts is all that he should have done in response to the coronavirus, especially given his pretty active resistance to any further measures.