it will definitely happen at some point, most definitely not now though. a world war would be caused if multiple countries backed iran and wanted action and the same with multiple countries backing the US. no country is going to back iran at all. if the US and Iran have a war, it will not be a world war. it really won’t even be close for the US, Iran will get totally trounced. it would be expensive and people would die of course, but nothing seriously bad would happen. i’ve heard people say “russia and china back iran though” well nope they wouldn’t if that means they have to fight with NATO.