In the United States, border zones are any areas up to 100 miles inland from a land border or coast. The majority of US population and cities are in border zones and the border rules apply to them:
Like most parts of the law the details are very complex. So, in fact there is a huge difference from being within 100 miles of a border and having just crossed one at an airport.
Or to quote your link: Border Patrol, nevertheless, cannot pull anyone over without "reasonable suspicion" of an immigration violation or crime (reasonable suspicion is more than just a "hunch").
In the United States, border zones are any areas up to 100 miles inland from a land border or coast. The majority of US population and cities are in border zones and the border rules apply to them:
https://www.aclu.org/other/constitution-100-mile-border-zone