Fair enough, I should have said “be a small island”. Obviously everything changes when you’re dealing with a population two orders of magnitude that of New Zealand: it’s harder to secure ports, harder to control contagion internally, etc. Moreover, the US never even attempted to harden its ports until the virus was already spreading out of control.

That said, the US has a lot of people crossing its land borders—even if it completely hardened its ports, outlawed border crossings, and was much better at reducing internal contagion, it would still have to deal with thousands of people who cross illegally and who aren’t going to quarantine for two weeks or abide by any kind of contact tracing programs.