Is Vietnam a U.S. ally

Answer 1

NO. "Ally" is a strong term and usually refers to a country with which the US has a military exchange and/or a convergence on particular political goals that are distinct from the binary relationship between the two states. The United States and Vietnam are on good terms, but since they do not have military cooperation and have minimal political goals outside of their binary relationship, it would be improper to call Vietnam a US ally.

However, Vietnam-US relations are relatively recent. A rapprochement between the Vietnamese government and the US government began in the mid-1990s, two decades after Vietnam defeated the United States in the Second Indochinese War (called the Vietnam War in Western countries and the American War in Vietnam).

Answer 2

No, not allies but no longer antagonists. Countries do not have to be allies to have peaceful diplomatic and trade relationships.