Security professionals have hypothesized many attacks against the anonymity of the tor onion and what you describe is pretty close to one of them.

If the NSA was to create tons Tor nodes (enter, exit, and relay), the onion may be broken.

Tor is by no means perfect. It is only obfuscating.

It is easy to see how this is broken if you click the TOR button on this thing and then imagine the TOR nodes say NSA on them.

I think it is more fun to imagine security this way (extremely challenging and like you are protecting yourself from the perfect attacker, and the NSA is a good face to put on the perfect attacker). People don't realize how much trust they are putting in their hosting provider, cell carrier, etc.etc. It's insane.