D. A Increase in nationalism in the US
Explanation: "The most notable result of the War of 1812 was an upsurge in American nationalism. At the war’s conclusion a French diplomat commented that “the war has given the Americans what they so essentially lacked, a national character.” The three-year conflict also resulted in increased funding of the peacetime military, better coastal defenses, a more secure western frontier, and a final confirmation of the Revolution’s outcome. The power of the Indian nations of the Old Northwest and Old Southwest was decisively broken, opening the way for white settlement across a broad front. Never again would European powers have significant influence with American tribes. The war also produced a new national symbol, The Star-Spangled Banner, which Congress made our national anthem in 1931. Most importantly, America’s independence and status in the world were reaffirmed, never again to be seriously challenged. ."
-nps.gov
