The most likely place for any major war in the world involving the U.S. is the Middle East. It could also be India-Pakistan as these have nuclear capability. Iran and Syria are likely enemies. It is unknown if the Obama administration would back Israel if open warfare breaks out. The U.S. should back Israel to the hilt, including committing our military, but our current government would most likely just support them diplomatically. The problem here is that Israel is just not big enough.
Israel cannot withstand much in the way of WMD attacks. It will not require very many WMD to injure Israel to the point where they will be unable to defend themselves effectively. This poses many problems for the U.S. Eventually WMD will be used. In the event of a WMD attack on Israel, retaliation can be expected. If a WMD attack occurred in the U.S., would we not do the same? Yet the position of the U.S. would be seriously damaged if Israel were to fall. We will need Israel in the next big war as an ally and as a military force to help tie down enemy forces. In addition, we will need Israeli offensive capability and experience. Additionally, the U.S. will need bases throughout the Middle East. It would be far better if we did not have to take those bases by storm. In other words, we will need our bases in Afghanistan and Iraq.
We should not give up any bases in Iraq. We need to have Iran on a two front war, if hostilities ever broke out. We will need an armed front with Syria just to interdict any forces that would be moving against us from there. India will most likely be an ally, even if just a pro-U.S. neutral.
This is all guesswork. However, history has demonstrated time and again that conflict in the form of open warfare is NOT obsolete. Conflict is as much a part of humanity as breathing and eating. Some conflicts have issues that have no peaceful resolution. Slavery is an excellent example. Sooner or later the issue must be resolved and warfare is the most decisive way to accomplish this end. As a result, big wars break out from time to time. It has been more than 60 years since the end of the last great open conflict. The time cannot be far off, and the issues present within Islam and the Middle East are so important and vast that it can be considered surprising that the constant warfare that is present has not grown to a much larger, more decisive level prior to today.