That last bit must have been either a joke or a lie, because he doesn't even do that on his own properties. Note the charts above. He has not even made an effort to hire American workers at his own properties. Out of the last 144 workers hired, one has been an American while 143 have been foreigners imported to work for Trump.
This is an outrage, and a huge broken promise. Are there no Americans who want those jobs? I imagine there are plenty, but Trump doesn't want them. He wants foreigners. Why?
I suspect it is because those foreigner workers will not complain about the poverty wages he is willing to pay, and they won't try to unionize. He's afraid American workers might do both.
Trump's campaign promise to put American workers first was just campaign propaganda. He didn't mean it. These charts (from Vox.com) expose his hypocrisy.