By "never permanent", I mean that every populous majority is permanent only within its world. But globalization keeps expanding everything, so the new players will "kill" them off. For example Austria-Hungary had the German-Hungarian majority, until globalization flooded them with Slavs and Romanians, today that country doesn't even exist. Or for another example, the Native American Comancheros(?) were a solid long term majority Texas group, but the white settler group eliminated them. We introduced the Chinese Exclusion Act to "defend" our group 100 years ago, but now there is nothing to stop that either.
We white Americans may contain many political groups, yes, but now globalization have extended over us too, and external groups (e.g. the Chinese) can potentially make us history like the others above. Then, protecting group rights generally, and specifically the rights of the American identity against an international (Chinese?) majority will be the key for our survival.
Does this logic work?