Joseph,
1. Where did you find that one about Yiddish being an “international language spoken by Jews”? Most Jews are Sephardic and DO NOT speak Yiddish. Most Ashkenazim also do not speak Yiddish except for words that crept int other languages.
2. What benefit does someone receive from knowing Yiddish? In fact, a case can even be made (@CTl) that it impedes learning German, which is an important language in international business (while most Germans, especially business people, can speak English there are imporatnt newspapers and magazines written in German. A person who starts with Yiddish must unlearn pronunciation differences. Moreover, much of Yiddish comes from Russian, Polish and Hebrew. One who does not believe that there are signicificant differences should watch a video on YouTube where two men translate English phrases into German and Yiddish respectively. In fact, when the Japanese Interior Minister interviewed a rosh yeshiva during WW2 he needed an interpreter despite being fluent in Yiddish.