Where is that constraint coming from? "Death to [x]" is a statement of a desire.

"Death to Americans" would be a call for the deaths of citizens. Obviously Iran doesn't consider the typical American citizen to be oppressing them, so they are not interested in calling for that.

Someone yelling "death to America" could still be supporting the death of George W. Bush or Donald Trump, who are Americans. It could even involve combating many in the US military. That's still very different from calling for "death to Americans", because the target is the regime, not its citizens simply for being citizens.

But I still think you've raised an interesting discussion to have so I've tried to answer it.

In an ideal world, regime change. Relatively peaceful dissolution is preferable and possible (consider the death of the Soviet Union).

However, given the ruthlessness of the people with the most power in the US, I suspect they would gladly kill millions of Americans before even considering a peaceful surrender. People are shot by the state in regular protests, let alone one directly threatening the state (case in point - Jan 6 had a protester killed by police). So unless some interesting lucky opportunities open up (such as a military coup), the USA will (continue to) kill Americans to maintain stability, regardless of whether those opposing the USA kill a single American.

Given that situation, it sounds like any resistance to the US is bad because will likely involve deaths of innocent people. Yes, but the other side of the story is that to do nothing ''also'' results in the deaths of innocent people. To the people running the show, it's completely normal to oversee the constant atrocious social murder of many thousands each year through poverty, artificial scarcity of food and medication, healthcare denial and other neglect in the name of profit. We overproduce enough food to feed everyone, there's enough land and property to house everyone.

To do nothing is to allow many Americans to keep dying each day from easily preventable deaths. To fix that system will most likely kill many Americans in the process. You can almost simplify it down to a trolley problem - there's no clean solution whichever choice you make. But, for each of us, there is a correct decision.