I’ve always assumed that reenacting civil wars is a uniquely American pursuit. (There ain’t no way that Vietnamese guys get together and go through the motions of the Tet Offensive.) And it’s not just the American Civil War that people are reenacting—they do the Revolutionary War, the Korean War and World War II, too. There are a few major classes of reenactors, based on how hard-core they are, and a few types of reenactments, from living histories to scripted battles.
It turns out that it’s not just Americans who do this: the Brits get into the act. There are two English groups dedicated to reenacting their civil war, The English Civil War Society and the Sealed Knot, and I gather that the two are something like mortal enemies. There’s also a WWI group, a WWII group, and Vietnam group (!), though they’re not quite reenactors as we think of them here in the U.S.: they put on shows for special events.
It looks like it’s just an American and English thing; if there are any Vietnam War reenactors in Vietnam, I don’t know about them.