I've recently bought a second car here in California. It's a manual VW Passat 2003 1.8 petrol saloon. It's very nice.
Apart from the obvious difference of the steering wheel being on the left, its manual transmission has one important difference from the UK: to start the car, you must press the clutch.
The car can be in gear; you just can't start it with a gear engaged.
In the UK, one often accidentally starts one's car in gear. The car typically lurches and you stop trying to start the car. Sorted.
I imagine this thing in the US is for safety reasons. Purported or real. Maybe it's 'cos engines are bigger here. Maybe batteries are more tender. Who knows.