Several people in this thread are saying regulatory issues are a major cause. Can anyone elaborate on what those regulations look like? I've been led to believ

Several people in this thread are saying regulatory issues are a major cause. Can anyone elaborate on what those regulations look like? I've been led to believe that a large fraction of pharmaceuticals consumed in the US are produced either entirely overseas, or else active ingredients are (and this causes challenges for the FDA to actively regulate those overseas producers). Is it the case that in some Sanofi site in Frankfurt, the same insulin meeting the same standards is put into vials, some intended for the US market, some intended for other markets around the world ... and regulations prevent someone from buying vials in the EU and selling them in the US? Like, the regulation is not only about the production methods or quality control?