Evidence?
H1-B requires an American company sponsor.
And your theory is that an American company won't sponsor anyone who doesn't already live here? Why should anyone believe that?
There are Indian and Pakistani outsourcing companies that hire bulk from their own country and send them here. Or they hire people here who are family members of H1-B and green card holders. I think these companies should be stopped. They are thoroughly unAmerican. But most American companies who hold H1-B hire from the US. Its too hard to hire someone aboard and bring them here.