From experience, I can tell you, it's not an easy task. If you want a job there, when you are not from the United States, you have to show some incredible background (Academics, Works, Projects), something they can't find anywhere else.

Also you should apply for the big ones, which are the ones, that will go for the hassle of the paperwork for the work visa.

I'll leave this link, so you can dig deeper.

https://hn.algolia.com/?q=work+visa#!/story/forever/prefix/0...