https://www.torproject.org/static/findoc/2020-TorProject-For...
https://www.torproject.org/static/findoc/2020-TorProject-For...
The US government has different parts with different goals: https://www.washingtonpost.com/news/the-switch/wp/2013/10/05... (paywalled). IIRC, the NSA has interests in conducting surveillance, and the State Department has interests in allowing liberal foreign dissidents to defeat surveillance.
It is worth being aware of course, but to my knowledge we have no evidence that Federal law enforcement has used anything other than old fashioned detective work to solve any Tor related cases.
There's always the possibility of parallel construction, but I would expect some reasonable evidence supporting this in some high profile busts.
They can either spy and let it slide because 1 guy buying weed on whatever replaced the silk road isn't worth that, or they can find the guy, arrest him if he's done something big enough and invent a way they found him. Hell, they could even say they found him on clearnet, the guy isn't gona go "your honor, i sure did buy those illegal drugs online but i used TOR so how did they find out"
My current biggest reason to believe TOR isn't breached on a massive scale is that snowden had nothing to show about it.