I think traumatise is a very strong word and it very much depends on the status of the relationships at the time and wider potentially supporting factors.
A cheating husband?
Yes, in the context of a very strong, supportive relationship, I'd be very shocked and would find the experience traumatic. Upshot is it would probably involve not just the loss of the relationship, but my home and having to share time with my children.
No, if the relationship was already dysfunctional and rocky and whilst the losses above would still apply, I might consider that a fair (but hard) trade in respect of being independent and demonstrating to my children that you have no obligation to stay in a shitty relationship. So upsetting yes, traumatic, no.
Parents moving 10 hours away (flight time) at 18?
Yes, if I had had no other strong support network around me and the practicalities of visiting hadn't been considered. At that age I think I would have felt very bereft and abandoned, especially if I had no "home" because it had been sold to fund the move, without any alternative.
No, if I had other close family locally (Older siblings/Aunts/Uncles/Cousins) who were supportive and actively engaged in my life and my parents had budgeted for regular visits and planned to keep in close communication via online means. Also that even if the family home had been sold a "crash pad" was still available to me and them in the UK.
Re: my latter paragraph this was the experience of a friend from school. She was fine. Parents moved to Dubai for work. Family home sold, but a lovely apartment purchased in the UK for her to live in and for them to stay during regular visits and they also funded regular trips for her to Dubai where she stayed during school then Uni holidays. On Skype (as it was then) every other day to catch up and she was very close to her maternal Aunt (and cousins) who lived locally who was in situ in case of an emergency and spent a lot of time with them.