There was an act. It was known as the Sherman Antitrust Act.
Most of them wanted to be neutral but some wanted to side with the Confederates or the Union
Many states passed new laws called Black Codes to restrict the rights of former slaves.
With the belief that African Americans we're inferior, they tried to make it harder for them to excercise their new found rights and freedom through the Black codes, Jim crow laws, and also other laws and organizations
Hope this helps
Because Congress has the power to decide if we go to war or not