Japan’s Prime Minister 主语.
is appealing to 谓语.
the Japanese people 宾语
to unite to overcome .目的状语.
其中有个从句:
overcome what he says,is the worst crisis his country has faced since the end of World War II.
overcome 带宾语从句,he says 可以理解成 that he says 做为定语从句,
更一般理解"he says" 是插入语
What is is the worst crisis his country has faced since the end of World War II.
就是overcome 的宾语了.
这里面,
crisis后面也跟了个定语从句:(that) his country has faced since the end of World War II.
since the end of World War II.时间状语从句.强。。。he says理解成插入语，整个句子就容易理顺了那么逗号要么？插入语,通常有"逗号"的.如果定语从句,一般就不加了.