This is a nice thought, but both American and European multinational corporations don't give a fuck where or how something is made as long as they're making money. Many of the products sold by Mondelez in Europe are in fact made in Europe, and some even have headquarters and administration in Europe. The same thing is true in reverse for companies like Unilever (London) and Nestle (Switzerland) when they're selling in the US.

A better approach than scolding only 4 brands (when there are literally thousands you want to boycott) is to focus on buying as much of your food as possible from independent, local sources.