How did white Americans intercede America and then turn the greenlands into Bread Basket of the world ?

(i) The urban population in the US was growing and the export market was
becoming even bigger.
(ii) As the demand increased, wheat prices rose encouraging farmers to
produce wheat.
(iii) American settlers laid down railway lines, that made it easier to transport
grain for wheat growing regions for the export to European countries.
(iv) During World War many countries lost their production, so US fed
Europe.
(v) US President rightly said, “Plant more wheat, wheat will win the war.”