The American Flag
Naturally, the American Flag is symbolic of America itself. In the context of the novel, however, it is symbolic of the oftentimes unnecessary force that America goes to in order to exert its will and what it wants across the world.
M16
The M16, which was an assault rifle manufactured for U.S. military personnel, is a powerful symbol of the U.S. military and U.S. military might. It is likewise a symbol of uniformity; almost every member of the U.S. military was issued an M16, living up to the name "G.I." or "Government Issued."
Saigon
Saigon is symbolic of an oasis of sorts for American servicemen and their wives to escape the tumult of war and find peace somewhere that was a lot like the United States.
War
The entire novel is an allegory warning against the dangers of getting involved in foolish wars. The United States didn't really need to get involved in the Vietnam War, the novel argues, and had no business entering a sovereign country. Many lives could have been saved if they hadn't entered Vietnam.
Trying to find community
Perhaps the most significant theme in the novel is trying to find community. Each of the women profiled in the novel is invariably trying to find a community which they could integrate themselves into. They were in a new country and didn't have any friends to support them. And each of them consistently made an effort to connect with people they had something in common with.
