My parents and grandparents were the same way viv-a- vis Japan, the loathing and disdain were permanent artifacts of the war, although the attitude with respect to Germany was more ambiguous.
I recall my grandfathers and father expressing great respect, even admiration, for what they ( the Germans ) did with what they had, while having exactly zero interest in ever owning anything they made.
Germanic ancestry is pretty common around here, including in my family, a lot of German prisoners were held here, ( as were the Japanese in a pretty large internment camp, which is only now getting some recognition as a historical artifact ) and that also probably contributed to some of the ambiguity.
It didn't help much that the Honda I bought was a true POS in every sense of the word, mostly shot after a few years. Lots of I told you so's about that.
I've bought one Japanese and German car and likely will never buy another. I don't avoid Japanese or German products, but I don't seek them out, either. I've had plenty of British cars, and will probably have more, but they were certainly no saints; plenty of reasons for Americans to loathe them, probably more so than the Germans.
Oh, well.