>All of this makes me wonder why a country would rely heavily on trade rather than produce a good deal of necessities itself. Maybe something's gone over my head but it seems like we've balanced that tradeoff between savings and security poorly.

Comparative advantage. If you as an individual had to be completely self-sufficient, you might just survive, but you'd eke out a very meagre existence. The same principle applies on a national level - it makes a great deal of sense for us to import food from places with lots of land and import manufactured goods from places with a lot of cheap labour, while exporting goods and services that benefit from our highly educated population and highly sophisticated economy.

This kind of trade has historically had a profound stabilising effect on international relations - you're far less likely to fuck with a country if it would disrupt a profitable trading relationship. You treat your customers with a level of courtesy that you wouldn't extend to strangers. Trade sanctions are a very severe but completely bloodless punishment for breaking international law.

Some issues are just inherently international. When Chernobyl blew up, Scottish farmers had to pour their milk down the drain. Back in the 70s, sulphur dioxide emissions from German and Eastern European coal smoke were destroying Scandinavian forests. If you were so inclined, you could really make life difficult for your international neighbours (or vice-versa) without ever declaring war. Trade policy is one of the levers the international community uses to resolve these issues.

Isolationism would definitely make us poorer and it'll probably make us less safe.

>>7715
All of this.

Comparative advantage on a large scale is what drives international trade, but on a small scale it's why you call in trades rather than fixing every problem you have yourself.