This is fascinating. I appreciate Mitchell posting it here. This letter wishes for Palestine something that no Middle Eastern country is close to achieving. As you point out in your introduction, the authors of the letter, North American Jews who sufficiently trusted the US constitution to feel safe (although there was still widespread discrimination in the 20th centruy), felt that they also spoke for other Jews in democratic countries, including France, Italy, and Holland. Sadly 20 years later, those Jewish populations were decimated by Nazis. The main usefulness of this particular discovery and other letters is for people to see that Zionism was not a belief that all Jews subscribed to. I have a letter written by my grandfather in 1943 which says this: As to the future of Palestine, it is our fervent hope that what was once a "promised land" for the Jews may become a "land of promise" for all races and creeds." This is still the fervent hope of many.
You know what I think about Zionism? I do not think that Zionism would dissolve the Jewish problem or any other problem. In my opinion it might only aggravate certain already complicated issues national and social in the Near East...But here is my ideology in a nutshell: we cannot solve national or social problems by creating new artificial states and boundaries. The Treaty of Versailles has taught us plenty. But blind reactionaries do not want to see - because it is their survival not to see and they will not see the truth because it means the elimination of that class and their privileges.
If there is any promised land for the Jews it is America. We make up less than 2% of the population and have what 12 senators and what 3 justices?