Just because they don’t ticket you for it, doesn’t mean it isn’t legally considered reckless. Cops often exercise a bit of discretion when deciding which ticket, if any, to write up. Some people just get out of tickets. I’ve never been that lucky, and I’ve never really driven particularly fast. A quick search suggests reckless is considered 15-over in CA, but I can’t find the specific statute.
To answer your question, I’ve lived all up and down the east coast and TX.
The only threshold that will automatically get you a reckless driving violation in CA is over 100 mph
Texas has no defined speed threshold
Alabama, where I lived previously on the east coast, has no defined threshold
The guideline for officers in CO is to consider a reckless driving ticket at 26 over the limit and above
I could keep searching individual states but I guess my point is there are many states where 20 over is pretty much a common thing among drivers and not typically punishable with a reckless driving charge. I haven’t spent much time in the northeast, perhaps things are different there.