Most deadly snake in the USA is the Eastern Diamond rattlesnake - but that's not as bad as the Black Mamba (Africa) or the Cobra. The Australian Taipan produces vemon "six times more deadly than that of the Indian Cobra" according to Jeremy Seal's excellent book, the Snakebite Survivors Club. The number one slot for venomous land snakes goes to another Australian inhabitant, the Fierce Snake, which, thankfully is not very fierce and attacks rarely. But the ultimate prizewinner is thought to be the Hydrophis Belcheri family of underwater sea snakes which are ten times more poisonous than any land snake!