There have been several wire manufacturers making PE over the years in the US and your source is correct, it's down to just one main supplier now.I've a funny feeling I know who your source is and have to say I wouldn't listen to too much scare mongering.This is usually the sort of thing put about by pickup makers who want to justify using cheap solderable wire over the more expensive plain enamel.
For the record, PE is still readily available.There is a tolerance of @+/- 8% on the wire but we buy in 50LBs at a time and grade it ourselves so that we use the most suitable for the given pickup.There has always been and minimum and nominal tolerance on wire and the industry has always worked with these tolerances. Whilst having PE coming mainly from one source isn't ideal, it simply means spending a little more time grading wire ourselves so not a problem.
Whilst we currently use US made PE there are several other sources outside the US so fear not-it's not about to dry up!
