Final answer:
The War of 1812 had political divisiveness due to Madison's inherited foreign problems and opposition from Federalists, financial constraints without a national bank, and inadequate military forces compared to Britain's superior navy. The Federalist Party's actions at the Hartford Convention and Britain's attention split with the Napoleonic Wars were also significant factors.
Step-by-step explanation:
The factors contributing to the political divisiveness and the inadequate execution of the War of 1812 by the United States include President Madison inheriting foreign relations issues from Jefferson, leading to a reluctance but eventual engagement in war. Additionally, there was significant opposition within the country, especially the Federalist Party in New England which was adversely affected by the war and considered secession at the Hartford Convention. Moreover, the lack of a national bank made it difficult to finance the war, and the small size of the American navy, with less than 20 warships, paled in comparison to the British naval power.
The unpopularity of the war in the maritime-dependent New England led to a political resurgence of the Federalist Party. However, the radical actions of some Federalists, including calls for secession, branded the party as unpatriotic and led to its downfall post-war. Internationally, the British navy's impressment of American sailors and the turbulence of the Napoleonic Wars strained relations, but Britain's own preoccupation with the conflict against France prevented them from focusing their full military might on America, giving the U.S. an unintended advantage.