I was taught that the major downfall for the Roman Empire was likely caused by its size. Just like CHina it had no real empirical ambition past a certain point and tended to "Romanize" wherever they conquest-ed because they were in preference for their own culture. Thats why in Tunisia we find Roman baths and likewise why we have China towns, its a transplantation of their prefered cultural norms within a new environment. When the Roman first started to expanded past the immediate boundaries of the Mediterranean into Germania, Briton and Judea, conflicts began to arise due to a lack of ability to maintain unilateral function over its military and economic systems. In a modern day application with instant messaging and more advanced transportation one may expect they could have upheld their boundaries but whether to not they would have wanted to (beyond the economic benefit) is unlikely.