Numerous American Political Scientists Have Observed That The U.S. Constitution Is An Invitation To Struggle Among The Three Branches Of Government. An Example Of Such A Struggle Is/are?

The President is designated the Commander-in-Chief and Congress has the authority to declare war.
The President has the power to negotiate treaties while the Senate has the right of ratification.
Congress has the power to pass legislation while the President has veto power over legislation. The Supreme Court has the power of judicial review.
The President has the power to appoint Ambassadors and Officers while the Senate has confirmation authority.