They gained new rights because they had contributed to the overthrow of the French. They gained prestige because they had fought alongside the new settlers of their land.
During the 19th century, America had a strong reluctance to become involved in other countries alliances and affairs. Isolationists in America argued that the US had a different philosophy than European countries and the US should defend freedom and democracy by not being involved in such things.
During the Spanish-American War, the US remained isolated and the country fought the war without alliances and without fighting in Europe. But the mindset started to change since the motto of freedom and democracy was substituted by the US bringing an empire in the Caribbean and in the Pacific - the US had influence in the Phillippines, Puerto Rico and Guam -.
President Roosevelt had the big stick policy, he believed that the US should export its values and become a global power. At the same time, he defended that the US should avoid conflicts. President Roosevelt ended the isolationism in the US and started the modern American philosophy of acting aggressively in foreign affairs even without the support of the Congress.
B.) Retaliation by foreign governments.
Southerners feared that tariffs would affect their fortunes given their reliance on exporting their agricultural produce. Retaliation by foreign governments would have meant that they would lose out as imposition of tariffs would reduce demand for their produce
