The argument is fundamentally the same. The benefit outweighs the cost by a large margin. There are social and psychological reasons for not donating organs after death that apply to blood donation as well.
Setting aside the few religious exceptions, that is correct. This gets to the root of the issue. Whether the body is property of the family or of the state. I argue for the former. In the USA there has to be compensation for property taken by the state. There also has to be a public good argument in most jurisdictions as far as I know. Because the beneficiary of the organ is not the general public, but an individual, I do not see how this could work without massive revisions to state and federal law.
As far as I can tell, dead bodies aren't property in the US. They can't be stolen (although other laws would likely apply), they aren't part of the deceased's estate, etc.
