Sleeping in public is pretty weird in the US. Napping at work is definitely frowned upon, and napping in a coffee shop, public transportation, etc, is unusual but happens. It's not necessarily socially discouraged, just odd.
Honestly, it never really occurred to me that people sleep in public in other parts of the world.
And when it does happen in the US, you start to worry if the person is having difficulties, and whether you should help them by waking them up. Especially on trains.
I used to set my alarm on the Caltrain and sleep during my commute to the south bay every day. If someone like you had ever woken me up, I'd have been pissed. In months of commuting before I moved down to Mountain View, nobody ever did see fit to rob me of my precious last hour of morning sleep though...
That's right. I live in the US and never saw any problem with napping in the college library, but one time I fell asleep out in my car while waiting for my child's class to end, and someone woke me to see if I was ok. Well I was just fine until you woke me, thanks!
Honestly, it never really occurred to me that people sleep in public in other parts of the world.