We have fought useless wars and only a select few have profited from them. The money would have been better served be re-invested in our country. Peace makes profit for all people. War makes profit for select people. Also, people forget what the real power in war is --- controlling the debt of the war. If you borrow to go to war, then whoever owns your debt wins. Basically, the banks. Then finally, war is about sending the poor of one country to fight the poor of another. Want to see war end? Send the politicians and the sons and daughters of the politicians to go fight.
Though war-time economics allow for more jobs and the temporary prospering of certain industries, it is a major toll on governmental budgets, as more money has to be spent on the war effort, therefor straining the budged. If you look back at history, you'll notice that it is at times of war(or following war) that nations were at their economic worst. It benefits corporations, true, but it is very detrimental to the government - and thus, every service it provides.
However, I think that it's less the perpetual state of war(though it is no help) and more the fact that the US government spends obscene and unecessary amounts of money on the military(you spend more money on the military than on any other single thing, you spend more money on the military in a year, than NASA would spend in a century at the rate of its funding).
We have been a socialist oligarchy under Keynsianism since WWII.
Prior to WWII, we had a number of actual wars and national socialist efforts which contributed to the development of this reliance on our war-economy.
Prior to WWII it was WWI, then the Civil war, Manifest Destiny (tremendously socialist) and a smattering of armed conflicts leading back to the revolution.
America has not known a decade of peace in 100 years.
On the contrary , it is a fairly well-known fact that war time economies are some of the strongest due to the increased need for industry and labor. While true that the profit generated is highly concentrated, war is at least slightly lucrative for everyone who manages to benefit from new jobs in the manufacturing industry. However, despite the economic advantages, the ethics of financial gain through death and violence remain questionable.
The myopic view of war is an argument about the military spending required to wage war. That spending is dwarfed by the spending required to rebuild (to include rearming, too). The positive economic impact of direct and indirect spending is enormous and carries on for decades or generations in the form of things such as long-term medical care spending, maintenance of newly replaced capital infrastructure, long-term affects of subsequent related policy changes, etc., etc.
Life lost during war has a multiplicative positive impact on economies in that it is a crude form of population control. In welfare states, that means for every person eliminated during a conflict, there are thousands of never-to-be-born descendants who will never exist - and therefore not burden the state.
War is necessary to strengthen and support domestic and global economies.
I could also argue to the contrary, but "war is good" would be the winning side of this debate, in the end.
The question is more of an idealist feel good question than a rational one.
I don't know how many of you are into economic theory, but none of them discuss war as a major contributor to the deterioration of the American economy. And you want to know the reason why? Prior to the Great Industrialization, the economy did not fluctuate at all because by and large we were a very independent agrarian society. Only post Industrialization (late 19th century), has our economy evolved to what we know as business cycles where we have developed our modern understanding of economics.
Since the establishing of our current industrial economy, Military expenditures as a total of our budget have only gone down, where in the past it dominated more than 50% of the US budget now only compromises less than 20%.
So by all accounts the data literally points to the opposite, it was also this data point which Keynesian theory developed, which aggregate demand in all forms have various multipliers. While one can argue that military spending is or isn't the highest multiplier under Keynesian theory it would still be a bonus to an economy and not a drag.
For those non Keynesian out there (myself included) who don't see aggregate demand as the focus point. Military spending very often contributes to technological innovations. The dot com boom was was born due to the creation of the internet, which was developed by the military as a mean of communication. While controversial the Iraq war has advanced the technology of drones / drone intelligence, which are now being used within society and by businesses.
While I am not going to cover how military spending functions within every single economic theory. It clearly has a lot of reoccurring benefits within multiple theories. And while you may find a particular case, I'd say the burden of proof has shifted to the "yes" side to provide a credible economic theory demonstrating war's consistent negative economic impact on the US.
Bottom line is, the state of war is not the dominate theme which defines any form of decline in the American economy. In the case for the US war has either been neutral or positive for the US for various reasons pending on economic theory.