Why would the regime do this? Just seems utterly at odds with the measured approach with the other strikes and doesn't feel like a strong enough American connection anyway.
I'm not saying it was a SAM, I'm more inclined to believe some kind of accident, but just because Iran knew their response was measured doesn't mean they know if ours will be and just because there's been no retaliation yet by the US I do expect their military will be on high alert for some time. Keep in mind their retaliation to the assassination was several days after the fact so it's not like if the US doesn't respond in 15 minutes and Trump doesn't make a statement right then that everything is all clear and it's business as usual. Likewise the US is likely not going to stand down just because Iran said they were done.
Edit:. Still, accidentally shooting something down that originated from your capital's airport thinking it was an enemy aircraft is stupid as shit, I know dumb shit just happens but still, I don't buy it.
I expect them to give the boxes to France, we'll know more soon enough.