I could have written much of your post Sara (but probably not as well, lol ).
You may or may not recall the emotional rollercoaster I was on during the time just before and after repatriating back in 2004. I felt one step out of sync in England and one step out of sync here in the US.
Like you, I lost both my father and my grandfather (who raised me) while living in England. DH was involved in two start up businesses at the time. My oldest son was a toddler and I was pregnant with my little guy. Money and time were both tight and I didn't have the opportunity to travel to the US as I felt I needed.
At the time, I grew resentful. Moving back to US without my grandfather and dad here made me grieve all over again. I was so confused and blamed DH for being "stuck" in England.
Thankfully, I had lots of friends and really made a life for myself, the kids and us. Getting out and doing things was my saving grace. But it sure was tough for the last few years, and the hangover that remained for a while upon our return to the US.
But to sum it up, you are right. It's hard to fully understand and prepare yourself for life abroad. I moved to be with my husband, not to "live abroad". The challenges and dynamics of being an international couple are immense.
I don't know if we'll ever return to the UK. We certainly haven't ruled it out. There's always the possibility that DH could be transferred there (Ironically, the people who's house we bought when we moved last summer, work for the same company and were transferred to England!)
Though it's not in our radar, if it came up, we'd never say never.
*Edited to add:... I often forget that during my eight years in England, I didn't know any other Americans. I was there from '96-04. During my early days, the internet wasn't what it is today. I remember looking for American groups, but it was before UKY was around and I didn't find anything. THen I got wrapped up in kids, DH's businesses, etc. and it never occurred to me to look again as my life there was established. I actually found UKY a few months before leaving England while searching for info for filing the petition paperwork for DH's visa...
...sometimes I wonder if I'd found UKY earlier or met other Americans, if it would have made a difference by having people around to relate to.