Iranians chant "death to America" because of America's past abuses, such as overthrowing the democratic government of Mohammad Mosaddegh to install the dictatorship of the Shah of Iran and supporting Saddam Hussein's bloody war of aggression against Iran (hundreds of thousands of Iranians died.) This included direct support for Saddam Hussein's chemical and biological weapons programs. It's ridiculous to frame this as Iranian "mad dogs" vs. innocent Americans. They have every reason to fear foreign aggression. For example, this and this.

Attacking Iran again would simply be continuing the pattern of violent aggression the US has established in the Middle East for decades.