i do know what it's like since i live in a different country to all my family and all DHs family. (well aware that we are not single parents)
I didn't know anyone and actually moved in the last 2 weeks of my pregnancy (and had been fired from my job for being pregnant so the court case was ongoing the whole 9 months)
I made sure to talk to all the neighbours, join all the mum/baby groups etc etc. I made sure i talked to everyone i possibly could and when i finally went back to work, i had plans A through E (chef husband worked 6 days a week split shifts so generally unavailable outside of if they needed a parent at home because they were ill)
It is exhausting. But i pulled my weight at work, occasionally asking if i could rearrange meetings or business trips etc. Answer was always: nobody else asks for it (all men with mostly SAH partner or part-time working partner). It was a MASSIVE struggle.
Ultimately, for me, it was worth it. For OP (or anyone else) maybe not. Only you know. But bloody hell, for sure employers need to be more helpful than so many of them are. But WE need to be more proactive. Don't just say "can't make it" - say "that's difficult. How about this... solution A, Solution B?" If you are pushed out after trying to meet them at least half-way - then constructive dismissal is worth considering. Join a union. now. Mine was invaluable giving me advice and assistance formulating reasonable plans that a company would be churlish turning down.
My bosses, or even most of my colleagues, had/have no idea i'm in a union.