Let's see...
Europe? nope because we rely on Soviet gas.
Africa? Yeah right, they have constant wars there but nobody seems to care.
Israel? Too well defended. Except if they attack first. Which they have done before and again, nobody seemed to care.
South America? Yeah... right...
Oceania? Nope. Too damn peaceful.
So that only leaves Iran, North Korea and China.
North Korea has made such a bad name for itself that even China wouldn't support them. On the contrary, I'd imagine they invade it first to keep the US out. And since the ideology is the same nobody would have anything to say about it, plus the population would welcome them. South Korea and Japan would also win from this, not having to care about nukes anymore.
China, well somebody suggested a case of civil war. But considering just how tight security is (Falun Gong is a great example of how they deal with pretty much any level of unrest), no way.
So that only leaves Iran and it's the "best" option for an all out world war. They've been surrounded on all sides which almost gives them the right to actually own nuclear weapons for defense. The population is very much behind their leaders. Even the opposition would hate a "liberating US army". The Russians have so far supported Iran and an invasion would plunge the US deeper into recession, China would buy everything in America, raise the dollar, crash the US home economy which would then lead to war with China to recover the assets. By this time Russia would jump to the aid of Iran to get their hands on the whole Middle East. This would draw North Korea out, India might take advantage and attack Pakistan. Israel might nuke somebody or get nuked themselves, well... you got the picture.
Europe? nope because we rely on Soviet gas.
Africa? Yeah right, they have constant wars there but nobody seems to care.
Israel? Too well defended. Except if they attack first. Which they have done before and again, nobody seemed to care.
South America? Yeah... right...
Oceania? Nope. Too damn peaceful.
So that only leaves Iran, North Korea and China.
North Korea has made such a bad name for itself that even China wouldn't support them. On the contrary, I'd imagine they invade it first to keep the US out. And since the ideology is the same nobody would have anything to say about it, plus the population would welcome them. South Korea and Japan would also win from this, not having to care about nukes anymore.
China, well somebody suggested a case of civil war. But considering just how tight security is (Falun Gong is a great example of how they deal with pretty much any level of unrest), no way.
So that only leaves Iran and it's the "best" option for an all out world war. They've been surrounded on all sides which almost gives them the right to actually own nuclear weapons for defense. The population is very much behind their leaders. Even the opposition would hate a "liberating US army". The Russians have so far supported Iran and an invasion would plunge the US deeper into recession, China would buy everything in America, raise the dollar, crash the US home economy which would then lead to war with China to recover the assets. By this time Russia would jump to the aid of Iran to get their hands on the whole Middle East. This would draw North Korea out, India might take advantage and attack Pakistan. Israel might nuke somebody or get nuked themselves, well... you got the picture.