America fights all sorts of wars, even when it claims it does not, or has not authorized that war through Congressional action, of which, America fights those wars because it is essentially an imperialist power that insists that it needs to control or to mold the world in a way and manner, that is supposedly to its advantage, in one form or another.
The thing about unnecessary warfare, even when such appears to be valid or victorious, is that there are significant costs, both direct and indirect for that warfare, over and above the inconvenient fact that war can cause a considerable amount of blow-back, that might not be seen for many years, or even for decades. Those who fight wars, have to use personnel and armaments, of which, the cost of such is both direct as in the monies that must so be allocated as well as the deaths and physical injuries that occur – in addition to the more hidden costs, as in the debt incurred to finance these wars, that may take years or decades to be repaid, if it is ever repaid, as well as the psychological damage done to the soldiers that have been an integral part of that warfare, not to mention the strong possibility of civil unrest and protests by the people about that warfare.
That is to say, there is a definite cost to war, and therefore, those nations that spend inordinate amounts of money on warfare, of which, year after year, those wars either continue or new wars are engaged, take a definite toll upon the people and the nation. On the other hand, nations that don't go to war, and make it their point to avoid warfare, are not only going to see significant savings in monies, but also the people of that nation, will not suffer the ill effects of debt incurred or domestic military personnel having been killed or injured.
The above signifies that in this modern age those nations that avoid war, are going to devote more of their time and energy to that which is often more constructive for their nation and thus their people, as opposed to those that are constantly involved in warfare, which in its totality, is debilitating to the people, because the cost of war, is paid by the people through the debt incurred, which thereby takes monies away from valued domestic programs, and reallocates such to being paid to the military-industrial-technology complex, as well as to the dominant banking consortium, that the monies so used for warfare have been borrowed from.
So then, part of the reason why China's economy, as well as other nations in the ascendancy, have been able to take global market share away from America, has to do with the fact that China does not permit itself to get involved in warfare, though it could; whereas, America insists it needs to be get involved in an endless amount of warfare, thereby stretching itself ever thinner, without seeming to comprehend that its warfare is actually weakening America and making it more vulnerable, because whatever that is being supposedly gained from such, is outweighed by the negatives, which thereby permits countries such as China to become ever more relevant and stronger, at America's hard-headed expense.