I spoke with professors at Princeton and at UVA about this (granted, in theology, not biblical studies) and their take was not black and white. Generally, if you want to teach in the US, its a good idea to get a US PhD, but its not a shot in the foot to go to the UK. Depending on who you study with and the quality of your dissertation (in the UK that is) you could do quite well in the US job market (their words). I think also if you go abroad and want to re-engage the US academy, its important to stay up with it while your in the UK (i.e. doing you best to attend conferences, presenting papers, etc.).