gate/drive height US vs. UK

I'm currently a British Expat residing in the USA. Having sculled and rowed in the UK I have seen differences in rigging here in the USA. In particular boats seem to be rigged considerably lower here in the USA. When I left the UK and since seeing recent British coaching videos (see slide 12 of and also British rowers in e.g. the Olympics, most boats seem rigged such that as the drive takes place, the rowers arms are parallel (or close to parallel) to the water.

Can anyone direct me to a discussion of this rigging choice? or contribute as to why this difference is so noticeable?

thanks in advance for any responses, David