Ireland is NOT part of the UK.
The UK came into being when Queen Elizabeth I died without an heir, her closest relative was King James VI of Scotland, son of Mary Queen of Scots, who was executed by her cousin, Queen Elizabeth I (psycho devil woman with wooden teeth....yeuch!!). So James VI became King James I of England as well as James VI of Scotland, thereby uniting the Kingdoms, hence the name.
Unfortunately us Scots must accept some of the blame for the British Empire. Sorry world. But considering the vast amount of great things Scotland has given the World, I hope the world forgives it.
However before 1603, England was rampaging about by themselves.
IMHO, America is the new England.