Could someone tell me where the flasher unit is on the car, thank you
Behind the fuse-relay panel -- item 9 here: Ferrari Testarossa (1987) Parts : Table 122 - VALVES AND ELECTROMAGNETIC SWITCHES But the same flasher unit is used for both turn signal and hazard flasher functions -- if one works, but the other doesn't, the problem is not the flasher unit.
I don't know why there would be one flasher "for US" and another one "not for US", but I've never found a difference in the euro vs US wiring schematic for this system (so either should work in any TR). Might be a subtle as the flashing rate being slightly different -- but that's just a guess. What version is your TR? Have you checked to see if fuse #24 (10A) is blown? Do your outside electric mirrors work -- they also get +12V power from fuse #24. If fuse #24 seems OK, but these things still don't work, try unplugging/inspecting/wiggling/reseating the w connector at the fuse-relay panel -- large V (green) wire in w connector carries +12V from fuse #24 to these systems.