>>26
Words like "basic" and "anomalies" confuse you or something?
OK, let's try a different simplification: The climates of Eurasia are basically distributed in belts (tundra, temperate, (sub)tropic) that stretch out for thousands of miles (don't have exact numbers, but look at a map, you'll get the basic idea).
Pick one point, go ten thousand miles east (or west, depending on where you start), and the basic climate will be the same.
And so a crop that grows in one place, a livestock animal that thrives in one spot, or a tech (agriculture, construction, etc) that works in one place, can be transported thousands of miles along this belt, and everything still works fine. And surprise, surprise: that's exactly how these things spread for thousands of years.
All of this translates to a huge area of applicability that makes the US look small.