Congress passed the act to help resolve the financial crisis that emerged during the early days of the American Civil War (1861–1865). In order to bring financial stability to the nation and fund the war effort, the National Bank Act of 1863 was introduced in the Senate in January of that year.
The best answer for this question would be: C. disagreement about trade tariffs between the United States and Mexico. The United States and Mexico had several disagreements in the past, including the transportation of slaves because the nation was expanding west and the territory of the United States. Although, there was no argument about trade tariffs.