I don´t remember that one of us claiming what you say: impacting East Asia and the world?
facts remain:
gunpowder was invented in China.
Vietnamese imported the technique of making gunpowder weapons from China. some sources suspected Vietnam did it illegally. Ming China forbade any export of firearms.
improving some gunpower weapons such as handguns and fire lances were made in Vietnam.
Ming China learned the technique of crafting of improved version of firearms and warfare during the war with Dai Viet in year 1406, and from Vietnamese captives and volunteers who served in the Ming government and army after the war, actually after the year 1427. the effectiveness was proved during the Ming military campaigns against the Mongols.
not East Asia, but Vietnam contributed positively in the development of Southeast Asia: stop in expansion of Hinduism and Islams, while preserving Confucism and Buddhism, civilizing the barbarians in Vietnam and neighborhood, restoring peace and stability when the region flipped into chaos, stop the genocide in Cambodia, expelling western invaders the French and Americans.
Vietnam sees itself as a nation in SE Asia, with cultures and custom of East Asia.
by the way, Chinese are not immun against propaganda. China under Mao Zedong suffered political/economics chaos and millions of deaths.