system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did automatic transmission become the standard in the US while manual transmission is the standard in other parts of the world?
gpt
The first commercially available automatic transmission was developed in the US by GM. GM mass produced the first few cars with automatic transmissions in the 30s but didn't really start selling them until the second world war when they incorporated them into tank designs. By that time they had perfected the mass production system for the automatic transmission and were able to start churning out tons of cars with them. 

Other American car designers soon realized their popularity and tried to catch up. It became a bit of a race to market and popularize the automatic. Because US fuel prices are so dirt cheap compared to most other countries in the world the reduced fuel efficiency of the automatic was just never an issue.

Because the technology was first developed in the US, and US car companies were less involved in international markets at the time, it simply didn't catch on in other places. It wasn't until much later that European and Japanese car companies began developing their own automatic transmissions, and by then many of these respective countries simply decided they liked the manual transmission more.