Is the arrival segment of an IAP in PANS-OPS the equivalent of FAA's feeder route?
An arrival segment can be part of both an arrival route and a designated STAR. Both are protected with the same design criteria.

The STAR chart consist of designated routes linking the approach procedure with ATS-routes or exit points in Free Route Airspace (FRA). An arrival route is simply a collection of arrival segments which are not part of a STAR when it is not operationally necessary to publish the route using the STAR criteria in ICAO DOC 8168 Vol. II Part I, Section 4, Chapter 2. The non-STAR arrival routes are published on the Instrument Approach Chart (IAC) as part of the Instrument Approach Procedure (IAP). 

Here is an example from the Norwegian AIP: 



The dotted lines from AND, SJA, FS and EVD to the IAFs are arrival routes containing arrival segments. These are the eqvivalent to feeder routes in TERPS, as they are defined equally.