I will agree that Trump failed to address the Iran situation properly as well. He dropped the very poor agreement put in place by Obama but Trump failed to have a consistent policy which addressed Iran's continual aggression in the region and kidnappings across the face of the earth.
It is questionable if the Obama "denuclearization" agreement did much beyond allowing Iran to hide their program. Certainly when Trump dropped the agreement Iran openly moved to accelerate their nuclear program and stopped trying to hide it.
The real problem is Iran's proxy wars and aggression across the region which Obama failed to address in any manner except for funding it further. Shortly Biden will have no choice except to address the situation head-on --- which will likely require military strikes unless Iran quickly acquiesces. Obviously the time of appeasement is over.
The real victims here are the people of Iran... many yearn for freedom from the oppression imposed by the religious dictatorial Ayatollahs. There have been protests in the past but they were put down with force by the Revolutionary Guard and other agents of the Iranian government.
I get we could seven degrees of Kevin Bacon to get how Iran’s hostility across the Sunni and Israeli regions in the Middle East can be considered a threat to US national security, but directly it’s really not.
The nuclear weapons, that’s a real threat to national security. Those have to be dealt with.
So, just so we are clear I don’t agree with you in that we have to be fully responsible to stop Iranian aggression in the Middle East. I don’t really see that as a provocation for US military action on any scale larger than a strike here and there for humanitarian reasons or just to check them back a bit.