How did the involvement of the united states change ww2? be

The entry of the United States into World War II shifted the war by turning it from a war between roughly equal powers to one in which the Axis powers were fighting an industrialized nation that they were not able to attack or destroy their power of production.

monarchy doesn’t have to have the hereditary element. there have been elective monarchies in the past where you choose your king-for-life and when he dies elect someone else for the job.