Here's a "who owes whom what" analysis on Iran-US. I haven't watched any pre-70s events so ignoring those.
Iran owes :
Iran takes hostage 50 US embassy persons breaking all diplomatic rules and keeps them as prisoner for more than 1 year. The 70s.
USA owes :
US shoots down an Iranian passenger airliner by mistake and kills 300 on board during Iraq-Iran war. The 80s.
USA owes :
Shoots and kills Iran's military commander, second most powerful man who was on a diplomatic tour.
Iran owes :
Shoots down 200 passenger plane of Ukrain by mistake.
I have a feeling now both sides are equal. The diplomat hostage can be cancelled off against diplomat Solaimani killing. And airline downing with the other airline downing.
Now look for the future.