Complex sentence: Because the CRB was officially an American organization, the CRB was also necessary to assure that the food, once delivered to the CNSA was not immediately seized by the Germans and provided the international support necessary to convince the British government to permit the shipments.
Split into simpler sentences: Because the CRB was officially an American organization, the CRB was also necessary to assure that the food, once delivered to the CNSA, was not immediately seized by the Germans. The CRB also provided the international support necessary to convince the British government to permit the shipments.