1. Power to declare war
Congress, not the President, has the power to declare war. This ensures that the people's representatives are heard in considering when to send Americans off to war.
2. The regulate Commerce
This, known is as the Commerce Clause, is the foundation for much of the expansion of the Federal Government since the 1930s. It remains controversial in some circles but allows Congress to get involved in things you would normally think were reserved to the States.
3. Borrow on the credit of the US
The US has debt. The constitution allows for Congress to borrow to pay for things. We will see how this one turns out.
