He context that had created and supported the jeffersonian worldview (that of the yeoman farmer as the bedrock of american democracy and the american economy) disappeared by the mid-nineteenth century, prompted by a shift toward an economy based on commerce, manufacturing, and larger scale agricultural endeavors. what is your best explanation for why this change took place

The War of 1812--the war and blockades proved the US was not self-sufficient.

The American System developed after the War of 1812 when blockades and war with Great Britain proved the US was not self-sufficient economically. Relying only on farming held the US prisoner if they could not sell their crops to a manufacturing country. The goal of the American System was to become industrialized.