"if we do this is it really going to upset anyone involved in the region?"
I'm sure that was at least part of the "calculus".
As to the answer to that question is pretty much a big no, I think you are mistaken. Iran clearly does care that Soleimani was killed.... if for no other reason than they can now "legitimately' walk away from the agreement to not make nukes. Yes, they may well have violated that agreement anyway, but now they have a "just" reason to violate it.
At the proverbial end of the day, Iraqis probably don't care... though it might well be a rallying cry for many, and apparently is that >>> another anti-American rallying cry.
As to the rest of the M.E., it depends on the country but most won't care as they have their own concerns.
Ultimately for me, as I said before, I think it was a bad choice.... but I think we should get out of the M.E. anyway. I don't think it possible for "us" to "fix" any of it, so sending our soldiers to die for a wasted cause is nothing less than stupidity.
The only people in the M.E. that should be any concern of ours are the Kurds. They have proven to be good allies. The rest of the M.E. can and should go f__k itself.
And on that note: that is exactly why "we" should be developing alternative sources of energy. Specifically: The day that sand is more valuable than oil, is the day when the problems in the M.E. begin to fade away. "They" either get with the "program" and move into the 21st Century...or go back to being nomadic desert tribes... etc.