The circle does not contain any part of the U.S.–in fact, it does not contain any part of the North or South American continents. The circle is mostly water. And it contains the least populated country in the world (Mongolia). Additionally, the circle contains very little arable land, compared to other parts of the world, meaning the vast number of people within it need reliable, safe sources of nutritious food.
Why is this important to U.S. agriculture? It’s not, really. Unless you want to grow your market, make yourself and your industry or commodity more profitable, or become a larger part of a global economy. Or you dream of feeding the world.