It is easy to make a mess and harder to clean it up. Do you think WWII ended in 1945? If you are German probably not.
When I was a teenager and quite conservative politically, one constant theme was that the US could have stopped the Soviets from controlling Eastern Europe. With the signing of the peace treaties ending WWII, those in power decided to let Europe be split into 2 parts, they never explained whether they knew that the Soviets would install friendly governments in all the Eastern European countries, but they did little to stop it. In 1948 the Soviets decided to make a power play in Berlin and to stop Western truck traffic (which supplied the Western sections of Berlin). This finally moved the US and the UK to action in what became known as the Berlin Airlift. The success of that airlift let Stalin know that we would use power to make sure that he would not expand any farther. Forty years passed before the Soviet control of Eastern Europe ended and Germany was re-united. While many still think of VE Day as the end of the war in Europe, the residue of that war only ended in North Eastern Europe when the Soviet bloc was dissolved.
Let’s move to the Iraq war. We started it in 2003, the Army was quickly defeated and the government deposed. Over the next year the Sunni insurgency started. The US tried to suppress it and showed some success, but that all unraveled under the Maliki government.
Today we see the US expanding its action in Iraq. We are bombing ISIS targets and supposedly we will be training Arab soldiers. All of this is supposedly because ISIS is a threat to the US. ISIS cannot defeat Assad’s army in Syria, so it is not a direct threat to the US. The video showing several hostages are alarming, but in a real sense they aren’t anything new. Foreign born extremists have been a factor in Iraq ever since George W. Bush decided to shock and awe the Iraqis into submission. Most of those extremists have come from the Arab world and many have been paid for by money from wealthy Arabs. Osama bin Laden was not a son of a poor family.
ISIS would be very easy to defeat militarily and even more so if we used the same tactics that worked so well in Germany (hint collateral damage was even more a part of WWII than it is today). The reason ISIS will not be defeated is that nobody in the region is willing to make those compromises necessary for peace. The Iranians created a sectarian government that the Sunnis hated. The Sunni Arab neighbors donated money to help Sunni Iraqis kill their Shiite neighbors. The US may have created a mess but the Sunnis and Shiites have kept pouring gasoline on the fire for 10 years. Until the Saudi Imams stop calling Shiites heretics this will not end. The Iranians aren’t quite as nasty (they don’t blow up Sunni mosques), but they didn’t realize the need to build a real coalition with the Sunni tribes.
In the end the split of Europe into Eastern and Western blocs was the right thing to do, even if it wasn’t a pleasant thing to do. I don’t have any idea of what will work in Iraq but bombing isn’t the solution and aiding the ‘good’ Sunni militants in Syria isn’t going to help.