

It may be zip code boundaries, given how narrow the NYC strip is. Some of the excessive jankiness in what was Nevada would be because no one lives on a lot of the federally-owned land reserves out there, so they don’t get their own post office, and the catchment area of some zip codes gets huge with weird boundaries.
Looks like some former USSR countries in Eastern Europe, like Ukraine or Lithuania, use +3 country codes. Was this always the case or was it changed after the dissolution of the USSR?