Vietnamese cultural tradition is an amalgam of the indigenous inhabitants, including people of the Tai family and the culture of the neighboring countries, the influence of which have waxed and waned over the ~2500 years of written history. To the North were the Han Chinese; to the East, the various Tai-speaking city states. To the South and East the Cham culture in the Mekong delta influenced by the Indian-influenced Angkor Empire. These civilisations were the major influences. Many small Hill Tribes were scattered throughout Vietnam.
Mahayana Buddhism entered the Vietnam from the North, Taoist and Confucian influences came from China. Indian culture contributed Hinduism. The SEAsian neighbors - Cambodia, Laos and the various Tai-speaking city states to the East were Theraveda Buddhists - for some reason, the two branches of Buddhism seemed to meet at the border.
The Northern regions (kingdoms?) were in a fluctuating relationship with the Chinese, an uneasy relationship which has persisted to the present day.
It may be useful to think of Vietnam as having three sections - the North with Hanoi as a major centre, the Central Part with Hue as a Capital, and ruled by succeeding dynasties of Emperors almost miniature versions of the Chinese Empire with a type of "forbidden city" and Imperial rites similar to China. The emperor did not abdicate until well after 1952. The southern third was most influenced by the Champa and Khmer civilisations. The Central part (Names of section Annam, Cochin and another, but it's time for someone else to take over. I haven't read about this since ~1970 and most of what I know is from "Fire In The Lake" by Francis Fitzgerald.
Another major influence was the French conquest bring Roman Catholicism. Enough.......