Given he seems open to hiring proper Americans within a week of the whole thing happening, it's perfectly possible he did, indeed, do the legal minimum+maximum of verification and was trying to do the right thing.

Since America is magic dirt where being born on it grants you citizenship, even if you never learn English or pick up on any cultural norms, it's perfectly possible to think you're just hiring people from "Little (Ethnicity)Town" where they insist on not fitting in.