Experiments of this kind had in both the U.S.and Europe well before the Second World War

你这句话差个动词,在had后,in之前.少了个been conducted，不好意思我就说嘛，这个很熟悉，我记得是道高考题还是模拟题来着。conduct experiment 做实验意思是远在二战前，美国和欧洲就已经做过这样的实验了。