As I understand it the Association of American Jewish War Veterans declared a boycott of German manufactured goods on March 19, 1933, this was in response to Hitler's announcement of a boycott of Jewish goods beginning April 1st. Later the American Jewish Congress declared a boycott on German goods. This was not "Jews of the world" uniting. Many Jews in America largely ignored the situation in German, as they were fearful of anti-Semitism themselves and wanted to sever ties to the Old World and be Americans.
I find it unlikely that this small boycott was a major cause of resentment against Jews. Hitler rose to power on a platform of anti-Semitism. He joined the German's Worker's Party (later the Nazi Party) in 1919, mostly because he was impressed with its founder, Drezler's, anti-Semitic rhetoric.
Not to be too long-winded, but anti-Semitism goes back at least, to Roman times. Entire books have been written on this subject, but some examples are the facts that Jews were blamed for the death of Jesus, despite their wielding no power of the Roman government, Jews were blamed for the Black Death (some theories hold that due to dietary laws and regulation on cleanliness Jews were less suseptible to the disease), and as early as 612 AD, Jews were banned from owning land in some areas.
On a final note, don't believe everything you hear. In 2000 it was implied that John McCain had illegitimately fathered a black child. It was completely untrue, but it probably lost him the South Carolina primary. If you are intersted in any subject, do your own research. Don't just believe what people tell you, including me!
