Here is the video in question. I know that, at least as far as Japan goes, there was minimal trading with countries such as Portugal, but can these countries have been self-sufficient nations without such trade?
This is a very old idea that has been slowly chipped away by ongoing archaeological discoveries.
Henri Pirenne argued that the Roman world ended and the middle ages began when the long-distance trade networks that crossed the Mediterranean were broken by Muslim conquests and piracy. He published part of this argument in the 1920s, and the rest was published after his death in the 30s. Even at the time, he received a lot of criticism for overlooking important data, and his arguments have since been almost entirely disproven (Muslims were big traders, and didn't end Mediterranean trade - to note one of many possible critiques). Nevertheless, his model has proven incredibly influential, and most medieval scholars have been shaped by his ideas. Especially the idea that the medieval world focused more on local trade, agricultural economies, and self sufficiency (as opposed to the commercial economies of the Roman and modern worlds).
But since the 1930s, archaeologists have found more and more evidence that medieval people traded a lot. At first, the evidence was just for high-status objects, the kind of trade that might have only affected the elites. It was suggested that this trade might not have been an actual economic system for ordinary people - they were mostly self-sufficient, while only elites engaged in large-scale networks of exchange.
But in the past decade and a half, a ton of new evidence (much of it from private metal detector finds, which are in some countries now being recorded in national databases, like the UK Portable Antiquities Scheme) has started to surface which suggests that, even during the early middle ages when people thought ordinary people's communities were very isolated, there appear to have been complex networks of supply and exchange that tied pretty much everyone into the trade economies that we once thought were only being used by the elite. See, for example, this volume.
While none of this trade is as extensive as what we have today, there was a lot of movement around the early medieval world. Craftsmen moved, materials moved, finished goods moved, and local villages like West Heslerton in Yorkshire, which can't have had more than a few hundred inhabitants (and probably not even that), were importing fish from the ocean (20 miles away) and exporting cattle.
The medieval world was very localized, and most people were farmers, but people traded.