Davey, First, as someone else pointed out, building an MC cartridge is not done by persons making 50 cents an hour. It is done only by an experienced craftsman. Among such persons in the world, only one that I know of lives in the US, and he is Peter Ledermann of Sound Smith. However, for his own good reasons, Peter has chosen to devote himself to Moving Iron (MI) and strain gauge cartridges, rather than to MC cartridges. For what it's worth, MI cartridges have many virtues that one may say make them superior (as a group) to MC cartridges, including lower moving mass. (But I don't want to open that can of worms.) So, if you must have a high end phono cartridge made in the USA, then bite the bullet and take a look at the Sound Smith product line. Grado also make superb "high end" MI cartridges, for that matter. There is no reason why high end MCs cannot be made in the USA, but the simple fact is that they are not, because no one has chosen to make them here.
For an added sense of exclusivity and bigger bucks, you might consider a Sound Smith strain gauge, as well.
For an added sense of exclusivity and bigger bucks, you might consider a Sound Smith strain gauge, as well.