But who are the "they" that you are refering to? The Vault Wiki states there was a limited nuclear exchange involving the Middle East during the Resource wars, as they were at war with Europe, and wouldn't bomb themselves, who did they nuke?
There was a limited nuclear exchange
in the Middle East. It's the Europeans who bombed them.
There was no "they" when the great war started. Nukes or not. Certainly not a "they" that could possibly threaten China or the US.
Europeans could have nuked each other, and some of them could have become vassal states of the US, China or the Soviet Union, and they were nuked by their respective enemies. And if Europe was left unharmed by the nukes while China and the US were nuked to cinders, Europe would quickly rise to power, even despite being in chaos after the Resource Wars, since it would have been in a much better shape than them.
None of the nuclear powers, seeing their own countries' imminent destruction, could really afford any developed country not being nuked, enemy or not.
Jesse Heinig, one of the FO1 designers:
One of the recurring themes of Fallout is that life will find a way to continue, albeit often under great struggles and with violence and suffering. It's not unreasonable, given this notion, to presume that U.S. remnant forces remain in parts of China, just as remnant Chinese elements are in the U.S.; and that other countries are similarly ravaged and war-torn, with survivors crawling out of the rubble. If Australia was untouched by the war, for instance, then presumably after 200 years they would have projected their powerful industrial presence and comparatively high population all around the globe to take control of any remaining resources, and the Enclave would find itself locked in a war with the Aussies. It's likely that some underpopulated parts of the third world escaped the full brunt of nuclear devastation, but since these would have been low-population unindustrialized areas anyway, they are not exactly in a position to take advantage of their "good fortune," such as it is. (I don't imagine that many nukes were wasted on the Sahara.)
The very first Fallout 1 timeline by Scott Campbell and Brian Freyermuth (from which all other Fallout timelines in existence are derived):
Other countries, seeing the US's missiles on their way, fire their warheads as well. What ensues is two hours of nuclear bombardment upon the earth's surface.
Emil Pagliarulo:
Tenpenny Tower was slightly inspired by Fiddler's Green, the skyscraqer in George Romero's Land of the Dead. But it was also an opportunity to introduce another character from outside the U.S. Allistair Tenpenny came to the Capital Wasteland from Great Britain to seek his fortune, so that alone tells you that the U.K. was also hit in the war. And if he came to U.S. to succeed, that says a lot about how screwed up Europe must be. So we just allude, a little bit, to the state of the rest of the world.
Tim Cain:
Q: What ever happened to the catholic church in the FO universe?
Tim Cain: I think it was nuked - the vatican that is.