Agree with Mike. Stand 50yds directly in front of your car with a Euro blinker on. Try seeing the blinker! Then try it at night with headlights on.
Probably why, in Europe back in the day, the Sport Paket included US style blinkers.
FYI, these "sport paket" US style blinkers were still available a year or so ago, and, were cheaper to buy (new) than the regular US style.