Some places are sticklers about the speed limit, and other minor offenses. If you’re local, you tend to know where they are, either from word-of-mouth or local news. Most places won’t ticket for going 5 mph over because a lot of judges will just throw the ticket out, especially if you come with a receipt saying you had your speedometer calibrated. In seemingly more and more places, 10 mph over is the norm. Some of that’s due to shrinking police forces. Pretty much everywhere, 20+ mph over is considered reckless driving.
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.