International Economics uses the same fundamental methods of analysis as other branches of economics because the motivates and behavior of individuals are the same in international trade as they are in domestic transaction.For example : Gourmet food shops in florida sell coffee beans from both Mexico and Hawaii ; the sequence of events that brought those beans to the shop is not very different and the imported beans traveled a much shorter distance than the beans shipped within the united states Mexico coffee shipments to Florida could be disrupted if the US government imposed a quota that limits imports; Mexican coffee could suddenly become cheaper to US. buyers if the peso were to fall in value againts the dollar.
Everybody knows that some International trade is beneficial. The most important single insight in all international economics is that there are gains from trade – that is when countries sell goods and services to each other this exchange is almost to their mutual benefit.The ranges of circumstances under wihich is international trade is beneficial is much wider than most people imagine.
 
Source :
International Trade Theory and Policy, Global Edition , Paul R. Krugman, Pearson 2015