Been looking at some of this stuff. There is evidence of high carbon steel SE of Ankara from 1800 BC.
There is also evidence that High carbon steel was used in weapons by 600 BC. Interestingly enough, the Romans used iron weapons til late in the empire. So the answer to the question may well be that in China the higher tech cities formed the empires and kept the tech. In the west, it may well be the reverse. The higher tech cities fade and what is effectively a bunch of low tech barbarians with a great logistical network and great fighting skill (Romans) founded the lasting empire, and set technology backwards. I guess it would be like instead of the Xin uniting China, it was some barbarian people on horses who were using bronze or iron weapons.
Interesting idea at least.
That could have been the case, but 1800 BC was the middle of the Bronze Age, when large stable empires (Egypt, Mycenae, and the Hittites) existed without threat from barbarians. There were plenty of other individual things in Europe, like the Antikythera Device, the large ships built in Egypt and by Archimedes, Hero's steam engine, etc, but the Iron Age didn't start until 1200 BC, steel smelting didn't start until about the late Roman Republic, water wheels weren't used until the Middle Ages, blast furnaces weren't used until the 1400s, etc. All of this was not delayed by barbarians (in fact iron smelting and waterwheels seem to have become widespread right after the bronze age collapse and the Roman Empire's collapse, respectively), while in China those technologies were in widespread use long before they were in Europe.