Correct: this is also why we ban importation of foreign food, so they Americans can keep at least BASIC knowledge of agriculture. Similarly, we require that air

Correct: this is also why we ban importation of foreign food, so they Americans can keep at least BASIC knowledge of agriculture. Similarly, we require that air transportation in US is only done on US made planes, so that US keeps at least basic knowledge of building planes. Without these measures, those industries would be gone.