America is a birthplace of aspirin, which has significantly contributed to the health of the mankind throughout the ages.

1. a birthplace of aspirin 应改为 the birthplace of aspirin，用定冠词表特指。又如：

New Orleans is the birthplace of jazz.  新奥尔良是爵士乐的发源地。

Virginia is famous as the birthplace of severalUSpresidents.  弗吉尼亚以作为几位美国总统的出生地而出名。

Florence was the birthplace of the Renaissance.  佛罗伦萨是文艺复兴的发祥地。

Athens is the birthplace of the ancient Olympics.  雅典是古代奥林匹克运动的发祥地。

2. 应去掉 mankind 前的冠词，因为mankind 表示“人类”时，其前习惯上不用冠词。又如：

The civilization of mankind has taken thousands of years.  人类经数千年才文明开化。

Since earliest times, mankind has been fascinated by fire.  人类自远古以来就对火很感兴趣。

According to the Bible, the whole of mankind is descended from Adam.  据《圣经》记载，全人类都是亚当的后代。

你的句子大意：阿司匹林最先在美国被研制出来，并在其后的漫长时间里对人类的健康作出了显著贡献。