puzzled~~~

Happy is he who dedicates his life to the well-being of mankind.
献身于为人类造福的人是幸福的。
其中who dedicates his life to the well-being of mankind.是he的定语。
倒装的原因：
当主语补语前置时，如果主语较长或结构较复杂，会引起倒装。

As settlers landed in America and established the United States as an independent nation,a new variety was added to the English language:American English.

he （who dedicates his life to the well-being of mankind）
这是主语he,后面是who引导的后指定语，形容he的

这句话正常语序是he (从句) is happy，现在反过来了，happy is he (XXXXXXX).所以是倒装。

你是问为什么阿, 刚才看错了以为你问为什么这是倒装呢. 哈哈， 倒装的目的：强调或者是在诗里面把韵脚弄到最后，这里我看是强调“happy”- 是快乐的！

As the immigrants in the North America continent founded the independent United States of America , there came another variation of the English language, the American English.

这就是一个一般表语从句，he作为先行词，在主句中做表语。没有倒装。

As the immigrants came to America and established the self-governed United States of America, English has it's another variation-Amer