US tail lamps delete the amber turn signal and use the brake lamps as additional turn signals which, in the opinion of some, looks terrible. As pre-work for installing EU tail lamps, the US coding must be changed to mimic EU coding so that the brake lamps and turn signals function independently. This is all well and good on the PFL cars, but apparently Audi, in their infinite wisdom, made an irreversible hardware change in the US FL units that sees the brake and turn lamps wired together in some way, rendering coding to EU spec ineligible.
The US “dynamic” rear turn signals (no option for dynamic fronts here as we don't get matrix lamps due to archaic FMVSS code) look absolutely laughable. The little strip dedicated to turn signal duty is dynamic, while the full brake lamp flashes normally at the same time. It looks like a seizure.