"death to america" does refer to an end to the US empire- not the American people. I've talked with a fair number of Iranians who dislike their own government and Americas reign of terror around the world.
From "the river to the sea" means an end to the apartheid government in occupied Palestine. It's projection from the murderous settlers that a unified non-apartheid state would mean their own extermination- because that's what they do to the undesirables in their unified state.
The government isn't the people.
Marg bar Amrika