Libertarianism improves foreign policy by promoting non interventionism while simultaneous promoting engagement (countering isolationism). Libertarianism is criticized for promoting isolationism, but that is not true. Libertarians wants engage in free trade with all, regardless of borders. And libertarians want to avoid wars to support the interests of large corporations that want to gain control of the resources of other countries - or defend the dollar from competing currencies. If we stopped protecting the dollar (petrodollar), then we would not be able to export our debt, and we would be able to rebuild our industrial base, instead of supporting a consumer-based economy that is unsustainable.
The Libertarian Party wants to protect American interests and will withdraw foreign aid to other countries. American forces abroad would be recalled and the United States would seek peaceful solutions to aggressive countries. Libertarians would be more protectionist to serve America's interests at home first and in foreign countries second. Foreign policies would improve in that taxpayer dollars would go to domestic programs.