Obama is currently in gridlock. He does not want to go to war because of the past mistakes made in the previous administration. Their mistakes also outweighed his to the point that the blame was shifted over by partisan Republican party members and supporters. An example being the so called Benghazi 'scandal' where a few American were left behind and killed in Libya. However many more incidents like this occured under the Bush administration and are ignored. So how is Obama the source of all woes in the United States when his own Congress refuses to support him at all.
The president's powers are limited, and many other people are in charge of policy making. Sure the president basically makes an oath to take the heat when stuff goes wrong, but it's not right. What the president can do is very limited, and the economy is the result of many presidents.
I think that, the mainstream belief, is that the current president (whomever it may be) is viewed as the top dog who's word is law. This is rarely the case. Does he have large influence on decisions? Of course. Is he responsible for every decision, good or bad? No.
The president does not make decisions or laws on his own. The bill or law must first pass through waves of congress, senate, and other representatives before passed along to the president. The president then has the power to veto that decision, or pass it. If it is vetoed, it is passed back to the congress who may veto the president's veto, and enact the law anyways. So, it is more or less balanced out. The president's power is, in fact, limited.
Why is only the president blamed? Because it is easier to gang up on one man than a group of men. Everyone knows the current President, but how many people do you think can name three congressmen? People see a mistake, people blame the closest most obvious possible cause, usually the one that doesnt require thinking or research of some sort. Hence, the president receives blame.