As to the rest of your post....America never has bought much of anything, if anything at all from Cambodia, Nam, or the old USSR.
We have NO trade with Cuba and haven't, since the '60s.
Nazi Germany was another thing. The concentration camps were hidden from most people's knowledge and was NOT widely publicized...in the beginning. As a matter of fact, even though they knew about it all, the owners of the N.Y.Times mentioned concentration camps and other such horrors, exactly THREE, and then, it was hidden in back pages, during the entirety of WW II. And when Hitler first took over, he had been duly elected, had yet to invade Poland, so WHY should any nation have immediately stop doing business with Germany, Miss Cleo? :-)
During WW I, not only did American NOT deal with the countries we were at war with, but people like you, refused to deal with AMERICANS, even those who had been here from colonial times, who had German sounding last names. Some refused to buy AMERICAN MADE PRODUCTS ( sauerkraut, delkeral, etc. ), that were in any way associated with the nations on the other side. That was NOT a "good thing"!
Your lack of historical knowledge is shocking.
I have no words for you, nopardons.