The requirement is that a majority share of the company be foreign owned (I think it may have to be the founder's country but I don't recall the exact details), and that "substantial operational investment has been made in the United States". The latter represents having a office lease, having purchased equipment and furniture, etc.

The latter also will cause you to hear sums like $200k be quoted. Our number was higher than this when we applied (we raised our first round outside of the States), so I do not know if there is a lower bound. This whole process is not well defined and is very much an exercise in compelling storytelling to convince the Visa officer that you're not committing fraud.