Why are people so so so interested in looking back at centuries old behaviour that any reasonable person would acknowledge as being unpleasant, unreasonable and probably unwarranted.
However, they were different times in a different kind of world, and it just so happened that it was mostly the people who called themselves English were the ones who wanted to go to other parts of this island, and neighbouring ones in order to say that owned more land and were therefore more important. That's little more than accident of birth - big wow.
Like an earlier poster, if there is a sporting competition, and for whatever reason England are not playing (like the 6 Nations games, for example), I have always favoured Wales, Scotland and (Northern) Ireland in no particular order, and the same if there are any domestic football or rugby teams, like Celtic or Rangers playing in Europe. I can't tell you the number of times I have been verbally abused by some of the people from these countries in the "we don't NEED your support!" kind of way. I understand it's not NEEDED, but as I like sport of many kinds I have a right to decide which of the two teams I am going to favour for the duration of the game.
My husband is in the armed forces, and there more than anywhere you seem to get some really mixed up people - especially Scots. The number of times I've heard some of his Scottish colleagues on one particular day saying that they joined up to get out of "the shithole where they were born/brought up" (their words, not mine) meaning various parts of Scotland, but then after a few beers (or maybe even when sober sometimes) the tirades of anti-English sentiment all wrapped up with the dislike of government policies have really shocked me.
It is a well known fact (within the forces) that there is a disproportionate number of Scottish people in the Armed Forces as a percentage of the whole population, when compared to the percentage of English, Welsh and Northern Irish. I find that very interesting - not sure what it "means" though.