The constitution ONLY enumerates the power to the federal government to establish post offices and post roads. Period. Thomas Jefferson didn't even want a postal clause in the constitution to begin with because he thought it would be a massive waste of money. Spoiler: he was right.

If Bernie Sanders wants to make such a vast proposal he should do it the legal way and propose a constitutional amendment. Of course, he knows that will never happen so he'll just unconstitutionally let congress force it through if he wants.

Of course, it's all talk now because he's not the president.

If people want government high speed internet so bad they should be lobbying their STATE government because that is where the power in the constitution lies.