The U.S, government has three branches which is a way to guarantee none of them has too much power. The Congress has special ways to check the President and the President has special ways to check on the Congress as well.
The President can veto a bill he does not agree with. A vetoed bill goes back to Congress for further amendments or approval. However, a presidential veto can be overridden by 2/3 majority of votes in Congress. The bill then becomes law without being signed by the President.
This is an example of checking the presidential power by Congress.
