But it shouldn't be all or nothing. For example, although most of the world uses the metric system, I think in aeronautics they still use feet to measure altitu

But it shouldn't be all or nothing. For example, although most of the world uses the metric system, I think in aeronautics they still use feet to measure altitude. US could migrate to metric independently of the aeronautic standards. Additionally, I don't think that changing tooling should be a priority. Even in the countries that use metric system, we use nuts and screws measured in inches. They are usually called 1/4, 1/2 and so on ignoring the "inch" part. Also, in Venezuela, letter is the standard paper used, not A4. I think a good solution would be for the US to use metric to measure most of the things people and industries interact with (distance, velocity, weight, volume), but you can keep the old measures when convenient.