"Straight to Hell" is one of my very favorite songs by The Clash, and is my favorite song on "Combat Rock."
First I have to give you a little background. When the album came out, I understood the song just fine, but what I understood was distressing, so I did a bunch of research. This is what I found out.
So much of The Clash's music is very political, and "Straight to Hell" is one of their most political songs. Basically, it's a criticism of the United States and the official policy toward children who were fathered by US soldiers during the war in Vietnam. You see, the US government made it nearly impossible for soldiers who served in Vietnam to bring back their children and the mothers of those children. Many soldiers actually married the women they had children with, thinking it would be easier to get visas to bring them to the US, but the government said no. There was a whole generation of children, now adults, who were born to US soldiers and their Vietnamese wives or girlfriends who had to be left behind. The lives of those left behind were really miserable. Women were often disowned by their families for getting pregnant by US soldiers, and their children, who definitely look half-American, were discriminated against terribly by the Vietnamese people, often being beaten and even killed. Many soldiers tried for years to be able to get their Vietnamese wives and children out of Vietnam, but the US had a quota system, and very few were allowed to come to the US.
The whole tone of the song is ironic. Basically, you can take it as the voice of the US government telling those kids that they can go to hell for all they care, and that they aren't wanted in the US, and should just stay in Vietnam.
At the beginning of the song it talks about "speaking King's English in quotations" which is a reference to the fact that many of those children, as they got older, tried to increase their chances of coming over by learning English and becoming Americanized. Even that didn't help most of them. The line you are asking about is, "Let me tell you about your blood, Bamboo kid--It ain't Coca-Cola, it's rice." That's basically saying, "it doesn't matter how American you look, or how American you act and sound, or how bad your life is as an outcast over there, the blood that flows in your veins isn't Coca-Cola (American), it's rice (Vietnamese)." That's because that is how the US government justified their decision to deny visas. They took the position that since they were at war with the North Vietnamese, and since there was really no way to tell for sure if someone was from the North or the South, it would be dangerous to allow a huge influx of immigrants from Vietnam who might actually be communists or spies. They basically painted it as a matter of national security to not allow those women and children to come over, as they might be dangerous in some way, and might be enemy combatants, when the truth is that the vast majority of them were just simple Vietnamese girls whose only crime was to fall in love and have a baby with an American soldier.
The line, "There ain't no need for 'ya," always, even after all these years, feels like a kick in the guts to me. That's pretty much what those people who were left behind were told. The Clash were simply pointing out something which has sort of been glossed over in the history books: the United States got involved in a dubious war in Vietnam, didn't care that the soldiers were getting women pregnant left and right, and then made absolutely no provisions for those children who are basically marked for life because they are clearly of mixed heritage.
When I think about it too much, it really makes me mad.
I hope my explanation helps a bit.
huge Clash fan, researched what happened to Amerasian children in Vietnam