Answered

what was a major factor leading to the erosion of regional cultural differences in the 1920's?
1) development of television
2)growing popularity of radio and motion pictures
3)publication of novel by F. Scott FitzGerald and Sinclair laws
4)expansion of air travel after Charles Lindbergh



Answer :

There were several factors leading to the erosion of regional cultural differences in the 1920's, but the best answer would be "growing popularity of radio and motion pictures"