Original brainchild for Lebensraum explicitly points to Manifest Destiny: https://encyclopedia.ushmm.org/content/en/article/lebensraum. You can slap "lebensraum" and "manifest destiny" into google and also see the results for yourself. I admit say I'm not a well of primary nazi sources if that doesn't satisfy you.
So why is that what makes China so bad? Like most things China is accused doing of the US has done worse.