An avowed pacifist dedicated to averting war, Cummings' poem is an indictment of blind patriotism that accompanies most war efforts. In his own life, Cummings experienced the downside of war, being arrested on anti- war views which arose during the time of World War I and the Espionage Act. He never expressed a hatred towards the Germans, which was "supposed" to be done as the United States entered the war. The poem speaks out against "jingoistic" conceptions of Patriotic zeal and also articulates the condition of America as a nation that has gained its identity and place in the world at the cost of groups, such as the Native American. At the same time, the poem seeks to articulate a condition of freedom of thought and expression, an element that might not be as clearly spoken during the "fog of war."
I think e.e. cummings' purpose in writing "next to of course god america i" was to show his frustration with our country. When I read this, I can almost hear the sarcasm dripping from every word. Most of the images he conjures up are what the politicians try telling us around election time. If you are naive enough to believe all of the patriotic mumbo jumbo (or "by jingo by gee by gosh by gum", as cummings puts it), then perhaps you will think it's beautiful enough to die for your country. Therefore, I think he is criticizing America and the ways in which politicians go about promoting a false sense of patriotism in their campaigns. Perhaps he is even criticizing the country's entrance into war.
I am really not sure how this question is any different than your question that you asked about this poem a few days ago. After all, once you know the meaning of a poem, then presumably you know why the author wrote it. I assume that an author writes a poem to get his or her message across (in addition to wanting money, like the second answer from your previous question said).
So, I assume that cummings purpose in writing this poem was to criticize blind patriotism. I assume that he felt that blind patriotism is a danger to the world and that he wanted to push people more towards thinking about what patriotism should (in cummings' mind) mean.
I should point out that this poem was published in 1926, at a time when many American intellectuals were disturbed by the way that patriotism had been used to promote WWI and to suppress radical ideas within the US.