The short answer is yes, English is sort of the default setting.

In the 1200s, the English King Edward I, went to war with both the Welsh and Scottish (see the film Braveheart for more on this). He was pretty good at war, and he subdued the Welsh and the Scottish (though the latter rebelled and got independence back). The Welsh didn't really recover after the death of Llywelyn ap Gruffudd (their last King), but Edward made the whole thing permanent by giving his eldest son the title 'Prince of Wales' as heir apparent to both the Kingdoms of England and Wales. That still persists today, though the Welsh aren't keen and even 800 years later still think the English are awful

Scotland went its own way had its own kings until 1600 when the Kingdoms of Scotland and England (including Wales) merged together creating the 'United Kingdom'. This was because Elizabeth I died without children and her cousin Mary (Queen of Scots) had a young son called James VI who subsequently became James I of both - and this was eventually made permanent in 1706.

There are regions of England where local and national identity are very strong. My grandmother (from Lancashire) would get very offended if everyone thought she was from Yorkshire.... this was because the War of the Roses is still fairly recent. The Cornish can get a bit antsy from time to time and most people outside of London think London is awful. :o)