What events and issues have rallied Asian Americans of diverse backgrounds together over the past four decades? What have been the strengths and/or limitations of organizing politically as "Asian Americans"? Why?
I should start this answer by noting that I am an Asian American (half Filipino) born in 1970. This means that I have been an Asian American for all of the last four decades. My answer to this question is surely influenced by my perception of Asian American history during the time that I have been alive. In my view, there has been very little that has rallied Asian Americans of diverse backgrounds during these past four decades. This is due to the major weakness that goes along with trying to organize politically around the idea of Asian American identity. The major weakness is that we Asian Americans are so radically different from one another that it is almost nonsensical to say that we are a single group.
The only event that I have ever seen credited with bringing together Asian Americans of diverse backgrounds is the murder of Vincent Chin. Chin was a Chinese American who was murdered in Detroit, Michigan in 1979. He was murdered largely because his attackers believed that he was Japanese. This was a time when the Detroit auto industry was suffering badly due to its inability to compete effectively with Japanese automakers. The two white men who attacked Chin blamed the Japanese for their economic troubles and took that anger out on Chin. I have seen sources that argue that all Asian American groups coalesced around this issue.
In more recent times, some Asian American groups have coalesced around the issue of affirmative action. However, not all groups have, and this shows why it is so difficult to do political organization around the idea of Asian American ethnicity. The problem is that Asian Americans are not all impacted by affirmative action in the same way. It might be true that groups such as Filipinos might be helped by affirmative action programs. However, there are other groups, such as the Chinese, Japanese, and Koreans, are actually overrepresented in selective institutions of higher education. They do not want to have affirmative action because it is likely to take spots away from them.
This shows us the major reason why organizing around Asian American identity is very difficult. We Asian Americans are by no means a monolithic group. For example, Chinese, Japanese, and Koreans are typically seen as “model minorities.” They are seen as hard-working groups that will do whatever they need to do to get ahead. By contrast, Filipinos are more likely to be seen as similar to Hispanics. They (we) have Hispanic last names and look more like Hispanics than they (we) look like Chinese or Japanese. South Asians such as people from Bangladesh do not look like Chinese or Japanese either. They end up facing different issues as they take jobs such as issuing traffic tickets in New York City. In addition, historical relations between various countries means that it can be hard to get Japanese, Chinese, and Koreans (who are often thought to look the same and face the same sorts of issues) to coalesce even amongst themselves.
Thus, it is very hard to organize Asian Americans politically. This is why few issues in the last 40 years have rallied all groups of Asian Americans and it is why there is no Asian American political voting bloc to speak of.