Though, it’s a bit troubling that the example comes from the documentary era (it’s convenient to adjust them — you know exactly where to look), and that "any schoolchild knows" it, plus the example about the Opium Wars is questionable. It would have been better to pick something from pre-documentary Eurasia. Ah well.
Now here’s a little trick — let’s take modern Russia as State B, and as State A some generalized third-world state, let’s call it Bubustan (too lazy to pick a specific one), and look at the situation through the eyes of 30th-century archaeologists.
Exports from Bantustan to Russia are obvious — well, bananas, coconuts, coffee, watermelons, melons, cotton. Identifiable by seeds in trash heaps. And migrant laborers, identifiable by genetics and anthropology. Social status is also determined through characteristic damage to bones and ligaments and other diseases (indicating occupation) and through the mineral composition of bones (indicating diet).
As for Russian products in Bubustan, they’re hard to find... what does Bubustan even import — petroleum products (don’t survive), pulp and paper products (don’t survive), various consumer goods (China and the like), status consumption items (Europe and the US), sometimes grain (hard to determine the origin). And also weapons — they do survive and their origin is easy to establish.
And here we come to the next point — mass graves with traces on skeletons from Kalash, SVD, Makarov bullets, sometimes Soviet tanks and APCs. Most Bubustans prefer Soviet-Russian weapons — they’re both cheaper and easier to operate.
Well, and excavations in Moscow-Petersburg show a massive presence of Bubustans with low social status, employed in simple and heavy labor.
What conclusion would 30th-century archaeologists draw? Right — Russia conquered Bubustan, forced it to pay tribute, and took slaves there.
What makes the example of the colonization of the Americas good — there, only 2 clearly defined sides came into contact (the others joined later), they had no prior contact (easy to determine the time boundary), and they were at significantly different levels of development (easy to distinguish one side’s artifacts from the other’s).
Actually, there are only a handful of such examples in human history; in most cases, you have to analyze societies that interacted with each other over centuries or decades, evolved together, and moreover the interaction wasn’t 1v1, but within a large crowd of other societies with a bunch of mutual cross-connections (see the example of Russia and Bubustan).
And besides, politics and economics rarely stand still — today a brotherly people, tomorrow "fed up with the churki" and tanks in Tbilisi, and the day after tomorrow a partner in the Customs Union. And all this over a couple of decades, which for archaeology is the blink of an eye.
How to reconstruct all this without written sources... well, no way...