"What he seems to be saying is that if UK retains its links to, and the restrictions imposed on trade by, the EU, then a new trade deal between UK/USA would not be feasible."

Well I don't care. We do far more trade with the EU than we do, and will ever do, with the US, and it will ever be thus. And we won't have to lower our standards to align ourselves with the lower US standards in many regards. I'd really like someone to tell me, without using that hopeful and rather empty word "opportunities," how a patchy plethora of little trade deals all over the non-EU world, each one involving a tiny proportion of our overall trade, will ever be better than what we have now. And we'll still trade with the EU, but under far more disadvantageous conditions. Take your time now.