I think they assume that intending to kill someone is ALWAYS malicious in the US, regardless of your personal convictions on the matter. But yes, you are correct that you could be charged with murder without actual malice on your part (not that it is really inappropriate - the fact that you're being dumb doesn't excuse you for your crime).

By the US definitions, assisted suicide is potentially murder due to your intent to kill, unless your state has an exception, though it is more likely to be voluntary manslaughter. Involuntary euthanasia is a whole different kettle of fish, though.