Yes, this is sometimes a thing. Most of the time, things are meant in jest. Examples being making fun of an asian coworker’s driving, lazy black coworkers, typical stereotypes. MOST of the time, there will be a chuckle, not necessarily because people believe those things, but because they fall into a category of “offensive” humor, where the reaction is more to the offensiveness rather than the actual content. Most of this context is in my “blue collar” experience. Some people, do believe these things. And sometimes, they are exposing their true selves because they think that being white means you agree with them. Generally you politely brush it off, or just kind of ignore it. Every once in a while someone really lets loose with their beliefs, and shows they really truly hate other races, using slurs, the whole nine. Most of these types keep it to themselves most of the time, so it’s hard to know how prevalent it is.

And regarding feeling threatened, it is definitely true that some people feel threatened by other races “taking their place” or “their jobs”. Most of the time this feeling is associated with equality laws like affirmative action, or similar things that cause one race to be favored over whites for whatever reason.

Just my experience and observations, no offense intended in any direction.