I don't think 'too big to fail' covers it, exactly. I agree that Uncle Sam would be unlikely to come directly to the rescue were Tesla to actually approach bankwuptcy. But Tesla also is not GM or TRU in another, more important IMO metric: customer interest. Neither GM nor TRU had by-a-wide-margin record-setting $1k down deposits for a sight-unseen vehicle. Neither GM nor TRU are upending a massive established industry. Neither GM nor TRU are considered in nearly the same light in terms of consumer fervor as Tesla.
So my view is that if Tesla were to come close to failing, someone like Google or Apple, or Tencent, etc, would scoop them up and largely continue with the plan. We know this was essentially lined up in 2013 with Google but never actually executed as Tesla recovered.