Also I'm not sure how you expect to get hired or even pass the bar with no/limited understanding of American law if you do an LLB in the UK!
There are Americans who will be much older, have more life and educational experience, and have knowledge of American law applying for the same jobs.
So either do the JD or an LLM in the US if you want hope for a job, or just go the UK route, get hired by an international firm, and try to transfer to the US.