Do you know why Iranians were chanting "Death To America"? Because we toppled their democratically elected government in 1953 and installed a brutal dictator so that we could continue to pillage their oil.(1) When the mullahs finally toppled that dictator in 1979 they had reason to be angry with us. This is especially true because almost immediately afterwards, in the 1980s, we used our proxy Saddam Hussein to launch a war against Iran, in which over a million Iranians were killed. During this time we provided Hussein with the means to make both chemical weapons and biological weapons (2), which Iraq used extensively against Iran. I suspect if another country did the same to us, we'd be chanting "Death to XYZ" too.
(1)https://en.wikipedia.org/wiki/1953_Iranian_coup_d%27%C3%A9ta...
We're chanting "Death to Iran" - isn't turnabout fair play?
Perhaps. If we had just chanted slogans instead of launching an unprovoked surprise attack that killed hundreds of their leaders along with thousands of civilians it would be fair play.