Actually, many (all?) of them do have laws by that name, but I don't think any of them compel you to render aid. They protect you from law suits if you are providing aid in a nonprofessional capacity and don't exceed what a common person would have done. IE, no chainsaw amputations for a broken arm or such general stupidity, but if I accidentally break your arm pulling you out of your car while it is upside down in the river in February, you can't sue me.