England is a country within the United Kingdom located mostly on the island Great Britain within the British Isles.
So it depends on which of those things you refer to. Great Britain isn't a country, the UK is a nation composed of 4 countries, England is one of those 4.
Not being Irish, it seems both refer to the same place, but there is an Irish nationalist or unionist political statement being made when choosing one or the other, so one could be looking for one of these names and not find it, depending on what website you're using. Both are arguably "native" names.
The Netherlands vs. Netherlands vs. Netherlands, The.
Lots of people are ignorant of all sorts of things. The relationships of the former members of the (former) British Empire are particularly complex.
Languages aren't countries. Geographic locations aren't necessarily parts of a single country (contested territories are a thing), and immigrants to one location may not read/write the language of the location they live in. ISO 639-3[1] is language codes, and they are NOT ISO 3166 [2] country codes. There are fewer country codes than language codes, which tempts lazy people to use country codes for language dropdowns.
So it depends on which of those things you refer to. Great Britain isn't a country, the UK is a nation composed of 4 countries, England is one of those 4.