Final answer:
The American response to the Oregon settlement with Great Britain was marked by a sense of pragmatism as President Polk agreed to the 49th parallel boundary, despite some militant expansionists' dissatisfaction. This compromise was seen as necessary given Great Britain's strength and the forthcoming war with Mexico.
Step-by-step explanation:
The response by Americans to the Oregon settlement with Great Britain was complex, and it varied among different groups of people. Initially, there was strong sentiment for obtaining the entire Oregon territory, as represented by the slogan 'Fifty-four forty or fight!' However, President James K. Polk, an expansionist himself, ultimately negotiated with Britain and accepted the 49th parallel as the boundary, leading to some displeasure among the more militant expansionists.
This pragmatism was attributed to Great Britain's power as a nation compared to Mexico. Those who were satisfied with the Oregon settlement appreciated its strategic advantages, including the acquisition of Puget Sound and the potential balance between free and slave states. An accurate description of the American response to the Oregon settlement would be a sense of pragmatism among some Americans, rather than unanimity, as they prepared for war with Mexico and considered British power dynamics.
Option 'A' is misleading as the approval was not unanimous. Option 'B' does not accurately represent historical sentiment. Option 'C' and 'E' are incorrect as the Northwestern states did not join with antislavery forces to condemn the pact, and southern satisfaction was not specifically about the legality of slavery by the treaty. Finally, option 'D' is not substantiated by historical documents. The pragmatism of the response suggests a general lack of widespread fear that Britain would renege on the agreement.