I think it's just Trump's usual attempt at brinkmanship and a signal that he isn't* going to back down until he gets what he wants. Just like Greenland!
*Then again, TACO. Just like Greenland.
This really needs to be emphasized. Throw it in their faces at every opportunity. Maybe make it such a millstone around Leavitt's neck that Trump chucks her out with Noem. Lay it out in every interview and every mention of the news.
"Trump said he would not accept anything short of unconditional surrender, but his Press Secretary says otherwise!"
https://www.npr.org/2026/03/07/nx-s1-5739242/iran-war-oil-trump-israel-spain-economy-one-week
Lays out some of the spreading consequences and problems posed not just by regional countries that might directly suffer from bombardment, but also for diplomacy and Western allies as well as countries as far off as Sri Lanka and China. Then of course there's the global fossil fuels situation.
I would say to be a "world war" you'd need armed participants from all those places to be shooting at each other, but this is definitely not a nothingberder in terms of global consequences.
For those without a subscription, NPR is running a similar piece noting the contradictory reasons given:
https://www.npr.org/2026/03/07/nx-s1-5734381/white-house-messaging-iran-us-israel-war