The world's wealthiest, most technologically advanced (i.e. modern, in every sense of the word), and free society -- America, hence "head of the snake". Every region, country, city, or group which follows this pattern, would be "the snake". America happens to be a Western country which embraces Christianity, but neither idealogy nor religion would be a prerequisite for being part of the body that makes up "the snake". I think the key word would be modern.