I think it is useful to draw parallels, to understand the magnitude of what the US just did:

The equivalent would be if Mike Pompeo was meeting with the Japanese defense minister, Taro Kono, at Dallas-Ft Worth Airport, and a Venezuelan drone shot a rocket that exploded the convoy on the tarmac, killing both Pompeo and Kono.

What would the US do? What would the US feel? How would Americans respond to the killing of our Secretary of State, and a general from a respected ally?

Now, imagine if Venezuela had their soldiers on our streets for the last 25 years. Killing civilians with impunity. Driving around and ignoring all traffic conditions and rules like they own the place... and then killed Pompeo and Kono?

The magnitude of the US's assassination cannot be understated, and ANY and ALL responses from Iran could be considered commensurate with the level of dishonor and embarrassment this will cause them. They can't get ground forces to US soil, but I have no doubt every US Embassy in Asia, the Middle East, and South America are currently being targeted for massive attacks, at the very least.