If the US ignored it and does not take action, other countries are less likely to take action, because the U.S. is generally a leader on these things.
It's kind of like asking "If the US stops pooping in the pool, what's to stop another kid from pooping in the pool?" Well those other kids are a hell of a lot more likely to poop in the pool if they see an international leader doing it.
Also, by leading the way and showing how decerbonization is not only cheaper, but also healthier, other countries will be more likely to try to save money similarly.
Most places that are installing coal these days are doing it because of local corruption. It's a lot easier to grift off a huge project than it is off of small distributed energy. Seeing that the US is moving away from coal will mean that corrupt local officials will have less excuse to pick outdated technology that lets them get bribed.