I think it's more of a cultural difference rather than government one. Korea and Taiwan are democracies and managed to control the pandemic as well. The US government has the authority to declare martial law, but doing so would completely undermine people's faith in the government.
There is certainly a cultural element, but it is literally a legal difference as well. The federal government in the US does not have the same broad powers as the federal government in Korea. Remember the US is a collection of states that consented to let the feds take on certain powers while retaining many, whereas South Korea is “just” South Korea. Provincial autonomy in SK is not anything like the “state’s rights” issue in the US.
