Checks and Balances

Between the three branches of our government how does anyone come to the conclusion the President alone is responsible for the state of our nation with regard to finance, war, taxes... We have three branches which are checks and balances on each other. Congress could have imposed laws to protect us from greedy investors. The Supreme Court most likely wasn't brought cases for the corruption in our mortgage system yet. It'd be worth investigating if our courts had any opportunity to exercise their power over the issues of mortgage fraud or the legality of us being in IRAQ.
What action did the Supreme Court and the Congress take to exercise their power with regard to our biggest national issues? The effect of their Powers, the Supreme Court's and Congress', on these issues leaves open the question for how much impact will they have on future Presidents.
Is it a logical conclusion that the Supreme Court gets involved on an after-the-fact basis in the government process?