In Brazil there are three modes you can choose: the full one in which all assets are common, the partial one in which the assets from before marriage are separate but the assets from after marriage are common, and the separate one in which the assets are kept separate. A quick web search tells me that the default was full for marriages until 1977, and since then the default is partial (https://lucenatorres.jusbrasil.com.br/artigos/450042665/os-d...).

Not in places like California, where many HN commentators are. Everything by default becomes common ownership unless you explicitly take steps to establish otherwise, with only a few exceptions (e.g. certain retirement accounts). It’s a state level thing though, so there isn’t one story for the whole US.