That's the fallacy the article is trying to combat. The war in Afghanistan did not take away from our capacity to build infrastructure at home. It's not like all the construction capacity in America was busy building stuff for Afghanistan.
> The real limit on government spending was not some artificial debt ceiling, or the risk of “running out of money”, but the productive capacity of the economy and the risk of sparking either inflation, or a ruinous multiplication of bottlenecks and dysfunctional backlogs of unmet orders. As Keynes said, we can afford anything we can actually do.
But the discourse about the war (as in your comment) focuses entirely on all the things we could've done with that money, as though building bridges vs bombing people was a binary decision.
It's not. We didn't spend $5T on war and leave our infrastructure crumbling because the war crowded out our capacity to build; we simply have decided, through our politics, not to bother with the latter.
The irony is that MMT has been perceived as a progressive theory to encourage spending on social programs. But progressives are arguing against war using the same austerity economics that conservatives use to justify not spending on said programs. Meanwhile, nothing about MMT is actually left or right; in practice the military-industrial complex in our government is evidence that MMT works.