This part used to require approval by a judge. Now the FBI can just ignore that step.
You didn't vote for that judge, did you. But you voted for the people that appoint FBI. Who is more responsible to you? Warning: Intellectual honesty required during the next several minutes.
Only in the case of agents of foreign governments or foreigners. Even then it requires the prior apporval of the Director of the FBI.
This doesn't allow for a wide scale fishing expidition.
It doesn't allow for creating a firearms registry.