I did learn metric in school, did you not? I'm in Ohio, not sure if it's different elsewhere. Typically it was tied to physics and chemistry, but still learned it.
I use both metric and imperial for work. But the issue is changing every single street sign, updating all of our school material, etc would cost the country billions of dollars and it just isn't worth it at this point.
Searching for magazines is possible, though maybe a bit buggy. You can search for unfollowed magazines in the same way you would look through your subscribed magazines Pics related
There's currently not support for that in the app. Also, for right now you should refer to the Github milestones. They're more up to date at the moment.