I will say that the lockdowns in those countries didnt just magically work

because it wasn't the lockdowns that did it. First off you're looking at some island countries (and South Korea is effectively an island with how secure its border is with North Korea) with relatively small populations that were able to halt all international travel the moment they detected cases. South Korea also has experience monitoring and controlling these viruses. The lockdowns were also very targeted via contact tracing apps that honestly might be considered an invasion of privacy here, but it wasn't a national lockdown, just affected areas of cities.

New Zealand and Australia had similar responses to each other, but the important factor is they were able to halt all international travel pretty easily, only allowing in people who lived there and quarantining them for two weeks. their international travel is still basically on hiatus.

We should've halted all international travel, including travel from Canada and Mexico at the same time we blocked travel from China. A lot of our early cases were coming from Europe through New York City and then spreading out throughout the country. Even then it might not have been enough since it was already here and had been for a while, thanks to a lot of travel between us and China. When you're the global economic giant, you're going to receive a lot of travel. Remember, we now have confirmed cases in the country before we knew what COVID was. A family friend of ours died suddenly around Christmas 2019 from a disease whose symptoms would likely now be considered COVID symptoms.

Meanwhile Italy locked down and the UK did and it didn't go so well for them.