We have not met, so I write as a fan, not a friend.
As you make your way in life, you may find yourself working - if lucky enough to have employment - for bosses who are inspired, honest and kind. But you may also encounter those who are incompetent, underhand and tyrannical; if so, you will learn that for as long as they are your superiors your choice is essentially to accept it or leave.
You made a big thing about wanting to represent the Republic of Ireland as your country. I happened to support your right, as a man from the nationalist community of Northern Ireland, to make that decision, and I came in for a lot of flak from NI fans as a consequence.
It is true, too, that as the Republic laboured until almost too late to get even with, and finally beat, the none-too-mighty Kazakhstan in the World Cup qualifier, Giovanni Trapattoni's refusal to send you on seemed inexplicable. "Where is McClean?" the Guardian's online reporter asked at 71 minutes. That does not make the coach underhand or tyrannical, though it does raise a question about how competently he handled Friday's game.
In the context of your international career, however, he is your boss.
To send a tweet criticising your omission - from the team bus, if reports are to be believed - was a serious breach of discipline and would have been so even if your thoughts had been expressed without an expletive.
James, you have been a breath of fresh air at Sunderland since that invigorating debut as a sub in Martin O'Neill's first game as manager helped to turn the prospect of a humiliating defeat to Blackburn Rovers into a storming last-gasp victory.
You have shown Premier star quality with your ability to beat your man, deliver dangerous crosses, score with feet or head and back-track when duty calls. You are still a little rough and ready, but have far exceeded the measured assessment of Johnny Crossan, another product of Derry City with great Sunderland connections.
"I’d say he has half a chance of making it," Crossan said of you in an interview with Salut! Sunderland just before O'Neill gave you your chance. "He still has a lot to learn, but he is an out-and-out left winger who cuts inside very well, though he’s not then great on his right foot. But if he gets the bit between his teeth he could do well."
Few would deny that in your showings for Sunderland, you have indeed done well. I long to see you go on to emulate Johnny's record of 48 goals in 99 games for the club.
Yes, you had every reason to feel frustrated that no place was found for you against Kazakhstan. But you must learn to keep such feelings to yourself (and your loved ones if you must, provided you can rely on their discretion).
As a boy, you may have been an admirer of Roy Keane. He had admirable if sometimes over-combative qualities as a player and deserves credit for leading Sunderland back to the Premier League having taken over as manager with the team at rock-bottom of the Championship. But he, too, was utterly wrong when he launched a bitter, foul-mouthed tirade against Mick McCarthy - one of Trapattoni's predecessors - in front of the whole RoI squad even before a ball was kicked in the 2002 World Cup in South Korea and Japan.
Keane probably had a point when criticising Irish preparations for the tournament. He was entitled to think privately that McCarthy was not up to the job. He had no right to subject him to an abusive 10-minute rant and, whatever his blindly loyal fans back in Ireland thought, fully deserved his fate - sent home in disgrace. And the French football authorities were right to come down hard on ringleaders of the mutiny in the national squad against Raymond Domenech at South Africa 2010.
You get the drift, James. It simply doesn't matter how many mistakes Trapattoni, McCarthy or Domenech make or how poor their man-management skills may be. As long as they manage the team you play for, you owe them the same respect any employee owes an employer.
If you cannot give such respect, or if your belief in player power leads you to demand that it must first be earned, then let your boss know you no longer wish to be considered for international selection. But remember that word "respect": if you ever get cross enough to do so, try not to resign in a tweet or, as in the case of your Sunderland teammate Steven Fletcher when pulling out of a Scotland squad, by text message.
PS: I am pleased you issued an apology and hope you get a chance to impress your boss in tomorrow's friendly against Oman. I also hope you then come roaring back to Sunderland and help us beat Liverpool on Saturday evening.