If the US would not tolerate anymore nuclear threats from NK, it should have made it clear from the beginning when DT threatened fire and fury.
After warning someone the first time, what to do, warn them again? If sanctions don't work the first time, they are never going to work. It would have been better not to warn and not to sanction. The only move immediately after defiance should have been action, then people would believe you mean business next time you threaten and fear even a hint.
NK is only testing its missiles and knows that it is curtains if they actually attack. Since they've flown missiles over Japan before and got away with it, the latest missiles should not be a surprise, they've done it before. Also, they're latest bomb test inside NK was inside NK. People do what they like inside their their houses. NK is not going to stop doing what they believe they have a right to to do.