A lower US corporate tax means: -Enticing US and global corps to move their HQ's back to US. -Moving more HQ's or manu facilities means more jobs. -More jobs means more tax revenue. -More tax revenue means lower deficit. -All of the above means more true economic growth (no artificial stimulus growth), a prevention of a further US dollar collapse, and hope that the debt can get chopped.
You forgot the 6th point:
- Companies lobby for newer ways to escape the recently reduced corporate tax levels.