What precisely is factually incorrect about the USDA training materials (except perhaps that slightly clumsy "emerging majorities" statement)? At the very least, the Pilgrims were "undocumented" aliens who simply imposed themselves onto indian lands, claiming them for themselves. They were certainly "outsiders" to the existing American residents who were, rightly as it turned out for them, a bit nervous about them but were generous to them nonetheless.
The USDA, as do many/most federal and other government agencies, does have a less than unblemished history when it comes to fair and equal treatment of minorities -- a quick read of the many various successful lawsuits filed against it, along with Congressional compensatory legislation for past wrongs will quickly validate that fact. So perhaps a bit of cultural, emotional and historical knowledge, perspective, understanding and sensitivity would not be such a bad thing to better understand, interact with and serve their varied constituents.