Hi Cadenza,
Sorry you are having such a rough time. I don't think it's one particular thing that makes it a difficult transition from social work in the states to social work in the UK . Like you my work was primarily therapy/mental health focused, and I found the transition to children services very challenging. I also think starting in the UK at a higher level makes it more difficult, even if you were qualified at such a level in the states.
You didn't mention it in your post, but I wonder if a lack of proper resources for families contributes to your stress level? It seems that you are trying to fill in all the gaps and is that because you are aware of what is needed and those services are not available?
Perhaps if you are able to take a step back and analyse the situation, you might find that the failures are not in you as a social worker, but rather the system. I'm not saying that it isn't important to always reflect, grow, continue our education, but sometimes it isn't just us as the social worker that is the failure.
I've left social work. I was a high level director in the states and then a team manager in the UK. I was not able to cope with the stress, the system, the lack of resources, the continued threat from the media that any day it might be you in front of the cameras. Even now, if I start to talk about my work I feel my chest tighten.
So please don't be too hard on yourself. I really don't think it's you that is the problem. I hope you are able to take a deep breathe and consider your options. I'm sure you are a brilliant social worker and that you will find somewhere that you are valued for your skills.