Interesting period indeed. Clearly the main factors in the West are the opportunistic rise of a great Islamic Jihad into a war-torn Eastern Mediterranean world, and the movement of the Avars into the Hungarian plains which let to another round of struggles between Byzantium and her neighbors; Constantinople, arguably, had the honor of being the climax, like it often does. Whereas in China the progression between the Sui, or as you call it Suo, and the Tang, in a way is almost seemless. It's quite similar to the transition between the Qin and the Han centuries earlier, the former fell because of the weight of its own iron grip on the people, the latter, while milder overall, build on the achievements that come with that iron grip without the burden of the crimes.

What happened in India at the time? The Gupta Empire just fell half a century before that, isn't it?