Chihoroのプロフィール

It became clear that Ken had attacked. It became clear that Ken attacked. この二つの文の違いを教えて下さい。

They have been to America. と　She has just gone to school. を否定文にするとどうなりますか？（中学英語です） They haven't been to America. She hasn't gone to school yet.でいいのでしょうか？