Dudes claiming they are "old stock" or "heritage" Americans. They'll even call other white people who's ancestors weren't here before the Civil War "ellis islanders" and invaders.
As someone who's ancestry has partially been here since the 1690s.. it's a crock of shit and silly as fuck.
Depends on the records kept by the family. Late 1690s, early early 1700s is fairly easy if records were kept and is not all that far fetched. I'm fortunate in that my family were indeed "old stock" and the records in that regard are fairly easy to find. As long as you're willing to do the research (and quite often other people have already done it for you i.e visited cemtaries and looked at early church records)
The most I've found is stuff from 100 years ago but it's spotty at best. Further back gets difficult because of that.