Complex sentence: The effect will have been unremarkable to north American drivers, but triggered comment in Europe, where single piece rear light units are fitted, rear indicator lights were and are normally included in their own separate part of the overall light cluster units.
Split into simpler sentences: The effect will have been unremarkable to north American drivers, but triggered comment in Europe. Here, even where single piece rear light units are fitted, rear indicator lights were and are normally included in their own separate part of the overall light cluster units.