I have been listening to and reading some stuff by libertarians who seem to think that in order to be truly free, one must be self sufficient. For example, many suggest growing one's own garden. I remember one especially silly reason for doing so was the great fragility of our food supply chain.
Now, put aside all the logistical reasons that one really can't be self sufficient (you'd need a lot of land per person, for one thing), and focus on the logical relationship between freedom and self sufficiency. I don't see how one follows from the other. Freedom, from the libertarian perspective, is a negative concept. It means that you are not coerced in any way; no one is invading your person or your property. It is a peaceful concept.
As freedom is a concept and philosophy of peaceful interaction, it is unrelated to isolationism. Of course, a person is free to try and be a hermit; no problem with that. You aren't free to take other peoples' stuff, though. But peaceful exchange is a fundamental part of freedom, and so to equate freedom with self sufficiency is to completely miss the point.