In order to fully compromise your privacy, the government would need to have control of _all nodes_ in your path, not just the entrance and exit nodes. (They _might_ be able to deanonymize some users by using traffic correlation using only entrance and exit nodes, but that is by no means a straightforward process.)

Tor also gives you a way to choose a specific exit node based on the country it is in, but I have no idea how reliable that is.

It is worth noting that with hidden services no exit nodes are required, since your traffic's final destination is running its own Tor-compatible node.

as Ajedi32 states, even knowing entrances and exits, it is SUPRHARD to figure out all the associations, but it has been done in the past for high profile sites. It is also not possible for them to monitor every entrance and exit, and it is akin to watching the entrances to a mall where everyone is dressed exactly the same, trying to identify who shops where. With one-off data, really hard. With regular or periodic data, the mystery is a lot easier to unravel.