As I alluded to in my post about pastry, there are various takes on food history. It can be analyzed from many angles, each with their advantages and disadvantages.
Most food history I have seen addresses the role the food plays within the culture. Not how the food got to the culture and what gave rise to the food's traditional role. Those last two issues are what I think is important about considering food in relation to the empires.
As the various empires wax and wane, they encounter foods new to them, very often becoming status symbols for their rarity and novelty. This establishes trade connections. Even as the empire wanes, these trade connections persist even if in a degraded and lessened state.
Without the growth of empires and the trade contacts they permit, food would be very isolated and localized. Even as empires wane, the food connections were often what helped drive the growth of the ex-colony. It had established trade patterns and partners.
In modern times, empires have become somewhat different. The French have an intellectual empire. It's not that they are the greatest thinkers of the world, but Escoffier explored an intellectual beachhead that gave France its' culinary power in the world, it's intellectual empire.
Similarly, the power of the Western world is pervading the other countries of the world, though not specifically in the colonial sense. This, coupled with the tradition of the French intellectual empire, fuels the Fusion cuisine. It is the current pinnacle of food of the empires with deep reflections about the trade and commingling of the modern world.
In the future, it will be easy to analyze fusion cuisine in the same way that we have studied Italian or Greek or French foods. But it would be a mistake to ignore that those three cuisines are interrelated, just as it would be a mistake to skip over the ramifications of Fusion cuisine.
I hope this doesn't hijcak the thread away from Cape Chef's questions that I didn't really address.
Phil