I don't think Dirk Nowitzki will be quitting his day job any time soon.
The video is obviously meant to be funny, and I guess the fact that he doesn't appear to know what he's even singing does strengthen that assertion. Adding to that, he's German after all and not even "born in the USA." And as far as I can tell, he's not even drunk in this video, so at least he's not too self-concious, which is a good thing.
Maybe the fact that he wasn't born in the USA helps make sense of what we are seeing above? I'm not entirely sure, but he at least gets an "A" for the passionate effort. Hopefully with that same strong effort rehabilitating his recent off-season knee surgery, he'll be back on the court before we know it.
[H/T: Ball Don't Lie]