Q: Why does a movie on my computer take an hour to download to AppleTV?

Welcome to the Apple Community.

Are you sure you are trying to download it from your computer. (i.e. through the 'computers' icon and not the 'movies' icon.

How so? If the movie is stored on your computer (iTunes) you access via Computers

Otherwise it is via Movies and as the device has no accessible storage it is streaming from the cloud where it requires a sufficient network connection.

I'm not sure I understand why playing content from your computers by using the 'Computers' feature is counter-intuitive.

Mark Secrist wrote:

 

Put the computer icon first. KISS.

You can put the icon where you want.

You keep changing the subject without closure, however if you did enter the correct password and it wasn't accepted, it was most likely the result of a networking issue with your network and nothing to do with whether or not the Apple TV is intuitive or not.

I found some movies that I purchased were still on the "cloud".

Yes, that's how it is supposed to work, movies purchased from the iTunes Store are always available through the 'Movie' feature.