For Israel, sure - Iran's been considered the existential threat to them, so yeah, that's the IDF's primary focus. Israel's a peer-level state to Iran (with wide error bars around peer, but they're geographically colocated and neither is large or powerful enough to fully overwhelm the other) - without the US's involvement, this would be a very, very costly war for Israel (and likewise, Iran attacking Israel would be very, very costly for Iran without the US too).

For the US, yes, we've spent a lot of time and effort focused on Iran, but our goal historically has been containment - Iran can't win a war against the US, but they're also not an existential threat to the US, so for us, the question's always been a cost/benefit analysis. Iran knows this, so their act for the last 40 years has been to keep the math on the US attacking Iran unfavorable enough to keep it from happening. This is why they never actually built a bomb - Iran's strategic position was calculated around not pushing Israel into the red zone while still making things too expensive for the US to be willing to bear the cost of attacking Iran.

Unfortunately for all parties, there's three primary flaws in the US's strategic posture: the first is we're too fucking big to feel like we have to do our homework anymore. We can "win" any military conflict shy of full open war against China insofar as we'll be the last ones standing, which puts the rest of the world in the position of having to accommodate themselves to us, not the reverse. The second is that as a people, we've got the shortest memory of perhaps any major nation on earth - the Iranian revolution was in 1989 and the coup was 1953, and to Americans, that's not just distant history, it's practically archaeology. Why would we worry about the Iranians? It's been months since they did anything. The third is we've managed to elect the physical embodiment of that short-termism into office and given him and his friends unilateral permission to do whatever they want in the national scale, which means there's no strategic calculus happening at all - whatever plans, frameworks, or understandings we've built over the last 40 years are in the dustbin along with the rest of the woke DEI crap left over from, eg, the Bush administration.

So, yes, the US has been planning for this for 40 years, but we've got the notable flaw of not reading our plans or caring what happened 40 years ago - as the old joke goes, "a serious problem in planning against American doctrine is that the Americans do not read their manuals, nor do they feel any obligation to follow their doctrine."