Oh @BrightPearlEagle, you sound to me like a very loving mother who has indeed become overwhelmed by the delightful devils of our teenage children - mine are now in their 30s and 40s - so somehow or other I survived that time, and you will too, you really will!
Please remember that there are - quite obviously - many mothers on Mumsnet, and for some of them they seem to particularly like hanging around the AIBU section here, and give other mothers advice that they wouldn't follow with their own children however much they may f and c words swear that of course they would.
There are also - probably quite a few - posters who don't have any children themselves, so they can't possible know the excruciating pain any mother inevitably goes through, from the very early, very lonely, sleepless nights of new babyhood, to the really scary occassions when our children have a very high temperature and seem to be too listless, to the sometimes broken bones as they get too more adventurous, and the being bullied if they are one of the less confident children. I am now in my 60s OP, and have been through my own share of worries and hardships, but the most overwhelming, the most exhausting, the most traumatic of moments that I have been through, have always been when my dearest, darling, children have been suffering from either physical, or even worse imo, emotional pain.
I believe that you are completely worn out, and, therefore exhausted, and overwhelmed, by the last 15 years, and if you are in your 40's you may already be entering the early stages of the peri-menopause. You have obviously been a very loving and caring Mum, which is why this has hit you so hard. Please believe me when I tell you that you are a brilliant Mum, and you sound like a lovely and caring person in your own right, and that every single loving Mum has made mistakes that we mentally beat ourselves up over!
I have not read anything that you have said on this thread BrightPearl, that makes your son sound like anything other than a very intelligent teenager, who is going through the most significant hormonal changes that the males of our species are ever likely to go through. I have actually always felt quite sorry for men that they can't have a little human grow in their bellies, starting as a tiny fertilised egg, with only a few tiny cells, which multiply rapidly, and then turn into tiny, little, exquisite, human beings, and even though I wish that nature had managed to find an alternative, but equally successful way, for the lucky ones of us, to be fertile every single month, from puberty to the menopause, without us having to go through such messy and often painful things as our monthly periods, I am extremely grateful that I was born a female.
(I wonder if my last sentence could be entered into the longest sentence in the English language ever written?)
Sorry for going off piste a bit, above OP!
Now, back to your obviously very handsome and charming son - I mean that genuinely, but I know that in AIBU in particular, some people are very proud of their talents at being sarcastic, but I am not one of them. I must admit that when you said in your thread that he broke down at your parents home, and cried for ages, my heart really ached for him, as of course, did yours, I know. Since that 15 year old girl thankfully admitted that your DS hadn't abused her, have you apologised to him for thinking him guilty of such a thing?
I can understand why you were worried, and probably panicked a bit, when you heard her tale, especially after your son's more recent behaviour, but as I have had to do with my own children in the past - but thankfully not too often - I think it is important that you apologise to him. I do believe that we should give our children, even young children, an apology when needed. I think it is very important that we can give meaningful apologies to anyone who deserves them, but particularly to our own children. Of course, please only apologise if he knows that you didn't believe him at first, if he doesn't know about that particular thought, then please don't tell him now! However, I do think that you should consider whether you still owe him an apology for sending him to his grandparents at that time, but only you know in your heart if that honestly seemed to be the correct decision for him at that time. and If you still believe it was, and if he seems to disagree with you about that decision, are you able to explain to him in an obviously loving, but not patronising way (I never claimed that any of this is easy!), why you, and his Dad if relevant, believed that to be the case. The fact that he felt able to cry in front of them, and ask for a hug, suggests that it might have been a fortuitous or auspicious decision anyway!
But, again, please remember that you are an amazing, but exhausted, Mum, who like all of us Mums who can be honest with both ourselves and Mumsnet, have almost certainly made some mistakes in the past, and will, unfortunately, almost certainly make some more in the future. We are not perfect, I doubt that even Mother Teresa was perfect all of the time, and yet she was still given a Sainthood, after her death 🩷
I really believe that raising children with our hearts full of love for them, can not lead to them being 'spoiled', I am certain that the only way they can be spoiled is if they are raised with little more apparent than indifference, and/or neglect, and/,or over/heavy use of discipline, and the use of discipline that is far harsher than whatever offence they committed deserved. I personally believe that not letting your DSon go on his sporting trip to the US would be a terrible and over the top punishment - and for what exactly? He didn't abuse that girl, and the rest of his behaviour looks to me like the behaviour of a child with a raging hormone battle happening within his own body and mind, and the actual unfortunate stress that an overachieving teenager will undoubtedly experience, before they have had any chance to learn from such a difficult experience. This sporting trip appears from what you have told us, to be the most important thing to him at the moment, and I think he definitely deserves that experience after studying for some of his GCSEs early - even it was 'only (?)' one.
Although I was bullied as a child, and not the one that everyone liked, even by all the teachers, I don't think that being very popular - and very clever on top of that - means that that a child has had a wonderful time at school, and with no pressures. In fact, students like that probably have more pressure on them than I ever did when I had bullies making my life miserable. I didn't have anything I had to live up to, but children like your son have an awful lot to lose mentally if they don't keep on making the effort to be the "life and soul of the school ground", and the really clever one their teachers and parents have probably almost taken for granted... If the trip was taken away as a punishment, what more could you use after that as a punishment in the future, because I worry that his resentment at not being understood, or seemingly cared about, could very sadly lead to much worse behaviour in the future. That is not supposed to scare you, I could be very wrong, but I am very worried that that is a definite possibility. I do know that that isn't the case with you, I know that you couldn't love him any less than you do, that your love for your children is totally unconditional, but I still remember as a teenager that I could convince my self of the worse case scenario quite easily, but to be fair, I was nowhere near as bright as you DSon, and unfortunately that hasn't improved much as I got older!
Your son is lucky to have you as his Mum, but going by my own children, he might not realise quite how much until he has children of his own 🤭 As a village member, I thank you for being one of the great ones @BrightPearlEagle 💐🍫 xxx
Ps. If you have managed to read all of this, thank you, it was no mean feat!