Final answer:
The least area of reform during Wilson's administration was in his foreign policy and interventionism, which deviated from his non-imperialistic promises and was overshadowed by World War I.
Step-by-step explanation:
During Woodrow Wilson's administration, the least area of reform (progress) was arguably in foreign policy and interventionism. Despite his initial intentions to practice a less imperialistic approach, Wilson often found himself engaging in overseas interventions in nations like Haiti, the Dominican Republic, and Cuba, mainly to protect American interests. Additionally, Wilson's progressive reforms domestically were overshadowed by the onset of World War I, which demanded a shift in national priorities away from domestic reforms to focus on national security and international affairs.