If it's just export controlled stuff(radar, dual use stuff), technically you can hire non US citizens, and IIRC it's actually discrimination if you only hire US

If it's just export controlled stuff(radar, dual use stuff), technically you can hire non US citizens, and IIRC it's actually discrimination if you only hire US citizens. But you need to get export licenses, which they might not grant based on the country of citizenship, and they require permanent residence. But let's be honest, it's pretty standard practice to require US citizenship.