Does setting locale before importing pandas help? BTW the Python 3 runtime attempts to do this when launching so it’d be great if you can test:
import locale
locale.setlocale(locale.LC_ALL, 'en_US')
import pandas
Also run RhinoCodeLogs after launching Rhino and see if a line similar to this exists. It should report your locale:
Info XX/XX/2024 XX:XX:XX AM [RhinoCode] Python locale is ('English_United States', 'utf8')