The US, maybe. But wiki suggests ETIAS (the EU one) was proposed in 2016 whereas the UK ETA idea was created around 2023, so ETIAS can't be a reaction to ETA - perhaps the other way round?

I'm not sure if, without Brexit, the UK would have ended up with ETIAS anyway - it's a "mostly Schengen but not exactly" thing so it would have depended on what agreement they came to.