I’d like to expand a little bit on the reason for quality on the Japanese side: At the end of the war, Japan was very low on resources and could not maintain large manufacturing lines with great inventory as typical of the mass production process innovated by Ford at the time, which forces them to maximize efficiency and minimize waste, both in terms of material as well as time. The Toyota Production System, or Lean as now it is known, was codified based on some core principles such as “minimize waste through continuous process improvement” and “automation with a human touch”, which allowed them to have great advantages in both efficiency and quality over the American manufacturers at the time.
I do disagree with your statement that Toyota quality was because of they “over-engineer” their product, but rather, something that is near opposite is true: Toyota is known to be very conservative with innovation and very much prefers to use tried and true reliable parts than make radical changes, that and the fact that they are the gold standard for manufacturing efficiency means that their defect rate will be very low. So, I don’t think their products are shaped by their culture, but rather their culture is shaped by their products.