Getting faculty position in the US: after Postdoc in the US or Lecturer in the UK?
Of course it is possible to switch from a UK lectureship to a TT, or even tenured, position at a US Research University. Being at a lower ranked "new university" in the UK, however, means that you likely not get a lot of research support and have a heavy teaching load. Further, the obsession with the UK REF will likely push your CV in directions that are not ideal for getting a job in the US. You don't mention your citizenship, but there is currently a lot of uncertainty regarding immigration and access to funding for non-UK citizens.

Overall, I would say that it will be easier, or more accurately, less difficult, to get a US TT position by spending another year or two as a post doc than as a lecturer with a high teaching load. US research universities just do not care that much about teaching and if you really need teaching experience you can always get a little as a post doc.

While a lecturer position might put you at a disadvantage, assuming it is a permanent lectureship in a UK city that you do not mind living in, having job security is a major benefit.