Well now, I wouldn't say that one should avoid all US built Steinways. That is, perhaps, a bit of a sweeping comment? I will grant that the Hamburg built Steinways are not quite the same as the US built ones (they are, in general, neither better nor worse, although they do have the snob appeal of being German made, like VW diesels), but to condemn all US built Steinways ... um... I don't know what to say to be gentle and kind to you, hbofinger, so I will say nothing at all about your somewhat unhelpful comment.
Now having said that, in answer to the OP, yes, there are years to be examined with great care: 1972 to 1985 (this is true of both US and Hamburg Steinways). These are the years when Steinway was controlled by CBS and the quality control was, quite frankly, poor (not so much a matter of inferior parts, but less attention paid to assembly, and poorer quality control on the wood used). The result was that some Steinways built during those years were excellent. Some were pretty ordinary. Some were, frankly, pretty horrible. Thus if you are considering a Steinway from that time period, the individual instrument has to be evaluated with great care.