Yes, but it is very unlikely, difficult and expensive - it depends also on type of the network:

permisionless (public blockchain) - it is extremely hard, it requires to take control over most of nodes (almost impossible), but some big countries may be able to do it… - question of cost effectiveness
permissioned (private or consortium blockchain) - it depends on the security of the private/consortium network, it is easier because there is much less nodes to hack and they are easier to track