Why on earth is the United States of America importing wheat? You could ask the same about oil and the answer wouldn't change. It's because of politicians who routinely violate the Constitution to push an agenda.
Back in the 70's Jimmy Carter and Congress decided it was a good idea to cap oil wells and place a moratorium on further exploration. They developed an "energy policy". Apparently it wasn't a very good policy, look where we are today. Now we're begging Saudi Arabia to increase output. The Democrats continue to block any attempts to extract the bountiful oil beneath our feet.
Fast forward to the current Congress with their ethanol subsidies and mandates. The farmers are taking food and using tons of fuel to convert that food into fuel. There is less food for feeding people, hence the need to import wheat.
I wish someone, anyone, would ask these politicians where in the Constitution are they granted this authority.