Why is the USA & Israel at war with Iran?

Because Iran sponsors international terrorism and is a direct threat to US allies in the Middle East, like Israel, and an indirect threat to the USA itself - especially if it gains nuclear weapons and can target its overseas bases.

Why does Iran sponsor intenational terrorism and want a nuclear weapon?

Because secular western countries persist in interference and regime change in Muslim (and other) countries and because Israel has nuclear weapons and is proven to a belligerent neighbour.

Why do western countries persist in interference and regime change?

Because they think liberal democracy is the best system for everybody, in every country, and so everybody must conform with it

Why must everyone conform with liberal democracy?

Because the liberal democracy leader of the free-world is the USA and it wishes to preserve its global hegemony above all else.

Why does the USA wish to preserve its global hegemony?

Because that's the best way to ensure that all power emanates from your country and your businesses, culture and financial controls can dominate the world, especially if your country also controls major resources such as oil and gas.

Ah! Of course. That's why. Iran just got in the way of why 5.