What source are you using? I haven't found any versions online that include an adjective before Stämme ("branches"), let alone a use of Rassen ("race") or Völkisch ("racial"/"national"/"ethnic"/etc).

Every German version I've found (here's a scan from Wikimedia Commons) reads:

"Das Deutsche Volk, einig in seinen Stämmen und von dem Willen beseelt, sein Reich in Freiheit und Gerechtigkeit zu erneuen..."

Which translates to:

"The German people, united in their branches and by the desire to renew their country in freedom and justice..."

This is basically a reference to German unification (before which the German people were divided into dozens or hundreds of polities). It's declaring their intention to rebuild a united German state (which they'd just overthrown in revolution) with new, democratic principles.

I think whoever wrote this might have imagined Stämme as "tribes" (which it's sometimes used for), and then translated that as "racial branches" — probably unaware of the connotations in English.

Hope that all helps! Translations are tricky and sometimes carry unintended consequences. Also let me know if I missed something, because my German is a bit rusty.