12V Resistor type coil.

[JayChicago]

As said above, I have read several knowledgeable ignition experts recommend the Bosch Blue coil. It's 3 ohm, so appropriate for 12 volt, no resistor.
Probably not made in USA. Bosch is a German company. Don't know if any coil is actually manufactured in the USA. Even Fomoco or Delco or Mopar electronic products are probably made elsewhere.
BTW, don't be tempted to go with a high performance, race engine coil. They can over-power the flathead's distributor and spark plug leads, cause shorting somewhere before reaching the spark plug.