Providing to your country both guns and butter, that is, war and destruction, while also providing the necessary food and material needs for your country is something that isn't possible without running some amount of monetary deficit. Anytime that you take people and resources away from producing and creating items that have utility and purpose to instead procuring labor and material to produce munitions and armaments, you have essentially traded food for guns, and warmth for bloodshed.
There are times when it is necessary to make that transfer to guns instead of butter, especially when your country is under attack, or when the world is in an unprecedented and dangerous peril. However, the decision that should be made is either guns or butter, not both, and the reason that the decision should be made that way is so that the people will readily understand that war has enormous material, spiritual, and sustenance costs. If, on the other hand, you deceive your people, by providing guns, while also providing butter, you will give them the misimpression that war is just another miscellaneous expense and its subsequent cost to society is little or nothing, whereas the truth isfar different.
Additionally, while these far-off battles are being fought in the here and now, the cost for these often unnecessary excursions in the form of payback, money and interest will not be borne by today's generation, but instead will be passed down the line to future generations whom neither voted, nor participated in these battles. This then also does not take into account the human waste, the psychological destruction, and death of the participants in these wars, in which all of this takes a huge toll on our country and the countries that we wage war upon.
In the meanwhile, no sacrifice is demanded or implied for our citizens as a whole, and since most members of American society are not part of our armed forces, they don't pay any particular attention to our oversea wars, and they simply are disinterested since it apparently costs them nothing directly, and more importantly all the bread and circuses are still available to them.
All this is done deliberately by our US Government, as it wants its citizens to believe that we live in some sort of Mr. Rogers ' neighborhood, in which all is well, we are taken care of, and that we all get along, except for those bad people that are far away and are dealt with by our professional forces using all appropriate means.
Guns and butter is a very bad story sold to us by our government to give us the misimpression that we can bring truth, justice, and the American way to the world by force, while fundamentally lying to the American people about what is really going on. Wars have consequences and should never be lightly engaged in. Wars also have tradeoffs and long-term costs, in which our government prefers to take shortcuts and to be disingenuous to its citizens.
The real reason why we have both guns and butter is that the government fears that if given the either/or choice, the public will desire butter, but the powers-to-be in government prefer war.