I'll back up the other folks who pointed out that long-term global trends in terms of violent conflict are basically overwhelmingly positive, but that only plays a little bit of a part in your main question, and doesn't really have much to do with US military adventurism during and since the Cold War
Is anyone willing to back this guy up and help convince me that there's any way life in the US would be WORSE with the $1 trillion spent in the middle east since 2001 re-applied to something more productive than fucking around in the desert? I have no idea how much loot we've sent to Israel but I'd pull the plug on that instantly as well. Unless you can convince me otherwise. Why not just have a department of defense that does what it's supposed to - defend?
Despite 9/11 being an obvious flash point it is difficult to use it as a cut-off for your question since a lot of the conflicts we are engaged in now have their roots and 'justifications' prior to 9/11.
For example, Iraq took place because of neoconservative/neoliberal ambitions that existed since the first Gulf War and the Bush/Cheney crew would have found a reason to do this 9/11 or not. The fact that they cynically decided to use 9/11 as a ploy to justify, and that the American people were stupid enough to buy it is largely irrelevant to the likelihood that such an invasion would have taken place anyway.
Our posture towards Israel, Iran and other countries in the region is basically consistent with what it was before 9-11 if not a bit more shrill.
Really the major difference since 9/11 is in the Afghanistan/Pakistan region, a region we had largely abandoned during the first Bush period. The idea being that Afghanistan is a fertile, lawless community for the extremist community around the middle east to gather and plan attacks, and having those elements in a lawless country next door to possibly the most unstable nuclear power in the world is a recipe for disaster.
So basically this is a really difficult question to answer in the post-911 context, but I would argue that the efforts in "Af-Pak" are justified however pessimistic I am about the outcome. Keeping nation states and nukes out of the hands of fundamentalist religious freaks (whether at home or abroad) is a pretty worthy goal and I can directly tie that to my own well-being and global peace.
YES
The Iraq adventure I have mixed feelings about, there was no necessity to fight that war at that time, however there may have been some value that may be weighed against the stupidity. The overthrow of Hussein and the sabre-rattling posture of the US in that region may actually have made some of the more corrupt authorities, particularly the ones that are ostensibly our allies, in the area change their posture towards the US. At the same time, we helped Al Queda open up a new front in their jihad, and through our various misdeeds along with our general imperial arrogance helped them greatly with recruitment and propaganda, as well as discredited ourselves to our allies, and our allies on behalf of ourselves.
NO
Iran - if our posture stands firm, and the people of that country continue to decide they don't want to be tools for an older generation's religious wars and end up overthrowing the regime
Yes
if it turns into another Iraq
NO
Israel - The Israeli right has clearly taken 9/11 as an even brighter green light to get aggressive against their enemies, they expect us to go along because they are our only solid ally in the region, but whether they become a welcome mat or a door mat really depends on what value that relationship provides to the US or it's interests. I think the Israeli experiment has been a net zero in both respects, and I applaud Obama's political bravery in actually telling Netanyahu that he has to play ball, not the other way around. The US is capable of establishing positive relationships in the Islamic world and does not need Fort Bible Camp doing more harm than good in that area. However, as I said before Israel has been our only solid ally, and due to our history of support since after WWII I think it would be shoddy to simply cut them off without giving them an opportunity to change course and get back on the right side of history. As of today, it's a
NO
So two nos, one yes, and one magic eight ball. In general I will again point out, that middle eastern oil and the flow of it into our wonderful machines has a major impact on our economy and quality of life, and that is an undeniable fact 'on the ground' despite the can of argument worms that opens.