Romania and Bulgaria are legally obligated to enter Schengen in future so yes it is a Schengen issue.
The UK on the other hand has no intention to join and don't intend to put visas in. This issue is more a Schengen than an EU issue.
The UK on the other hand has no intention to join and don't intend to put visas in. This issue is more a Schengen than an EU issue.
It has to be this way because when you enter the EU it is either Schengen or the CTA (UK/Ireland).
While technically Bulgaria and Romania are not yet in Schengen, they have to enter at a future time.
The Swiss, Norway and Icelandic visa policy IS involved because they also have to fill in the silly form and pay the fee to visit the US/Canada as part of the Visa Waiver Program or eTA but a US/Canada citizen can simply enter Switzerland or Norway (Schengen) without any forms or fees.
While Bulgaria, Poland and Romania have the WVP issue this isn't the only reason for these measures. This is on the agenda too (how they are not in the WVP) with the USA despite intending on being in Schengen.
While the UK/Ireland also has the ETA these negotiations don't have anything to do with it as they will not be imposing Visas on US or Canadian citizens.