Americanize country agnostic code

[tawandamoyo]

Partially fixes #1543

[anth-volk]

@tawandamoyo Unfortunately, there are quite a few points in the front end where the output of this API route is utilized, and they all refer to a "labour_supply_impact" or something similar. Would you be willing to Americanize those, as well? Otherwise, these changes will just crash on the front end.

[tawandamoyo]

@anth-volk , sure will open a PR for the frontend

[anth-volk]

@tawandamoyo Just updated this to deal with some merge conflicts on the API. After tests are run, I believe this will be good to merge, followed by the corresponding front-end fixes. Thanks for your patience.

[anth-volk]

Thanks for this @tawandamoyo! Before merging, https://github.com/PolicyEngine/policyengine-app/pull/2149/files will need to be reviewed and approved. Then we'll merge this, followed by that one.