The US has a lower voter turnout than New Zealand (significantly so until recent elections) and holds its elections on a Tuesday as opposed to a Saturday. Despite both countries having non-compulsory voting, there is a greater amount of friction for a potential voter in the US so if the choice is between a bad candidate and a less bad candidate then for many the inconvenience of voting will outweigh any desire to see the less bad candidate win.
The US has a lower voter turnout than New Zealand (significantly so until recent elections) and holds its elections on a Tuesday as opposed to a Saturday. Despite both countries having non-compulsory voting, there is a greater amount of friction for a potential voter in the US so if the choice is between a bad candidate and a less bad candidate then for many the inconvenience of voting will outweigh any desire to see the less bad candidate win.