I didn't remember anything about widespread nuclear war. The Arasaka-Militech Corporate war ended with both sides getting nationalized, not widespread nuclear devastation. The USSR still exists (though subsumed by Sov Oi), as does China (as evidenced by Kang Tao and you do a quest for someone implied to be a Chinese spy). Theres also lots of references to Europe being a haven for advanced Biotech (especially in the expansion) and there's advertising for holiday packages in Somalia.