The International Organization for Standardization (ISO) list of countries, does not list England, Northern Ireland, Scotland, and Wales as countries. However the ISO list them as sub divisions of the United Kingdon.
Internaly the Office for National Statistics (ONS) uses “country and Province” to describe what subdivisions make up the United Kingdom.
Great Britain (England, Scotland and Wales) and Northern Ireand are the four constituent countries that make up the United Kingdom. What matters is neither of the constituent countries are recognised individualy on the world stage. Apart from Northern Ireland if any part of the United kingdom breaks away it could collapse the what we know as the UK. This however is highly unlikely to happen.