Of course it endangers North America. These are tests to fine tune their missile system. Soon they will have the capability of either detonating an atmosphere or hitting a target within the U.S. They don't need to be very accurate. 

This is probably going to lead to the annihilation of North Korea, something that seems inevitable. When that happens, the US needs to step back and tell China good luck but this is your mess. We learned that winning a war means rebuilding the country the we defeated. We don't need to be on the hook for rebuilding North Korea not to mention the fact that millions will die when this conflict reaches it's conclusion.