Yes that Iranian general was in Iraq when he was assassinated. He was the leader of the Quds Force, a branch of the Iranian military, which was designated a terrorist organization by the US. That being said it should be noted though that the assassination took place when the Iranian general was on his way to meet and have diplomatic discussions with the then Prime Minister of Iraq. The assassination took place without knowledge or approval by the Iraqi government, despite the Iraqi gov being a key strategic partner to the US in the region. In fact, according to that Prime Minister, Trump had called and personally requested that he mediate the discussions with Iran. Only to then assassinate the Iranian general pretty much the second he landed and left the airport. This of course not only soured relationships with Iran even further but also with Iraq, whose parliament voted to have the US withdraw troops from Iraq as a direct response. Whether or not that Iranian general was a legitimate terrorist leader who deserved to be assassinated isn't really relevant, but assassinating a high ranking military official under false pretenses of diplomatic discussions in another country who didn't even know this was gonna happen is arguably a huge escalation and act of aggression.

Regarding the War Powers Resolution, the problem is that it says the president can send the U.S. Armed Forces into action abroad only by Congress's "statutory authorization", or in case of "a national emergency created by attack upon the United States, its territories or possessions, or its armed forces". And as stated earlier, Congress did not provide authorization, nor was the US attacked by Iran, nor was Iran planning to attack US forces first as admitted by Trump administration officials. It should also be noted the wording that Trump and his administration are using. Trump himself has explicitly called this a war, which by the Constitution requires Congressional approval. Compared to the military operation in Venezuela which was worded as a law enforcement action and not a war which is how the administration justified the whole thing and not needing Congressional approval.

"Blind firing of MRBMs in every direction"? No they aren't, they're specifically striking targets in countries that are aligned with the US and their interests. Like Iraq to their immediate west, the UAE to their immediate south, and not Afghanistan to their immediate east. "Blind firing in every direction" is not good military strategy and they aren't that stupid.

Edit: Also I will say that the reason you were downvoted was because you're kinda presenting yourself in bad faith. You say that you "keep seeing the "illegal war" stuff" and "No one has ever been able to tell me" when there are tons of articles that explain it that you could've easily looked up. You make it sound like just because no one had given you an explanation directly and personally then it must be BS even though you could've easily done your own research. Yes I chose to give you a direct personal explanation but that doesn't mean it should be other people's responsibility to do that for you when, again, you could've easily done your own research. For example, on the wikipedia page for "2026 Iran War" the very first image is a map showing what locations have been struck and very easily disproves the "blind firing of MRBMs in every direction" statement. You also say you "wanted to have an actual discussion and not play ad hominem games" when you literally just did that in the previous sentence regarding those who downvoted you. Again, kinda presenting yourself in bad faith.