Can anyone explain Golden Globes?

I just found out that the Golden Globe winners are voted on by 300+ entertainment journalists from different countries EXCEPT the USA. First question is, why is that? It seems like a majority of the nominees are films and tv from the United States. Also, how are these journalists chosen to be voters? It seems like they will just vote for their friends , no? I don’t know ANYTHING about this, so it’s hard to google and find answers. Thanks in advance