Interesting discussion, and it's great to see how such a controversial topic can be discussed so respectfully, as it should be, because there really aren't any absolute answers, just decisions with their own trade-offs.
My personal take is that I just don't see how in our modern world any country, even one as blessed as the United States with the characteristics Chris outlines, can truly prosper as a self-contained unit. Yes, we have a large quantity of natural resources, but not nearly enough to fuel our various industries, many of which would simply whither and die, and all their jobs with them, if you took away the resources and products they rely on from other countries. A few examples of materials we import 100% of are Columbian, Fluorspar, Graphite, Mica, Quartz crystal, rare earths, Rubidium, Thallium, and Thorium. I, like most, had no clue what these materials are used in until I looked it up, but they are critical to American industries such as steelmaking, lubrication, jet engines, combustion equipment, paint, cement, paints, glass, abrasives, etc., etc.
Another example is oil. Yes, we have huge quantities of it in the US, enough to be nearly "self-sufficient," but extracting it would come at a large environmental and safety cost (and I'm the farthest thing from a tree hugger), which is a big part of why we're importing so much of it. It would be great if we could come up with a competitive alternative, and I wish Chris and his company all the best, but people have been trying for decades without any luck. Gasoline is a near-miraculous material, so you're going up against Usain Bolt in the 100 meters, I'm afraid.
Yes, we have lots of systemic problems, but isolating ourselves from the rest of the world economically isn't the answer.