I don't see how self-sufficiency matters (unless war). In a globalized economy you want to keep the high-margin business and offload low-margin business to someone else.
I'm not an expert, but my understanding is that heavy reliance on imports increases the riskiness of debt, as external pressures and events can impact the debtor without recourse (whereas even in the event of a local industry failure, imports remain a stabilizing secondary option).
In an event of financial crunches, a self-sufficient economy should still be able to hold its own without dire threats from cut of essential imports. Its economic crisis could be quite bad but won’t be catastrophic, as in some well-known cases we’ve read about in the news.
