micky wrote:

The wires in my Toyota are much thinner than the wires in any of my
American cars were.

I think it's probably a modern vs older, rather than japanese vs
american thing?

Car manufacturers seem to use "thin wall" cables now, using a tougher
grade of PVC so that a greater %age of the overall volume of the wire is
copper rather than plastic. Probably reduced copper too due to lower
current requirements, as others have mentioned.