Some of the confusion here is from our history. This is my (likely confused) understanding:

James VI/I (https://en.wikipedia.org/wiki/James_VI_and_I) was king of _both_ England and Scotland and only later did the Union https://en.wikipedia.org/wiki/Treaty_of_Union combine the two. You might notice I've neglected Wales which was (considered?) part of England.

In any case, England is a country, yes. Also the UK is a country.