Question about PSOne compatibility

Hi guys, I just need a little clarification.

I was just doing some research and came across this article: http://www.vg247.com/2012/08/28/vita-compatible-psone-classics-full-list/

The gist of the article is that US gets 9 games while Europe gets 129 (at the time of the article, not too sure about now)

The thing I'm confused about is, would EU games not work on the US set, possibly due to difference in hardware?

Or can I download using my EU account via my PS3 and port it over. (It can be done. http://www.youtube.com/watch?feature=player_embedded&v=2YUhf_4P7vU)