What device in western countries allows ATC to get clearances or search flight plans automatically?
The European equivalent would be the Flight Data Processing System (FDPS). The FDPS receives flight plans over the Online data interchange (OLDI) / ATS Message Handling System (AMHS) from the Integrated Initial Flight Plan Processing System (IFPS) which is operated by EUROCONTROL. In addition local flight plan can be added to the FDPS. 

Aircraft operators file their flight plan with the IFPS, which checks the flight plan for correctness (syntax errors, route errors, etc) and determines whether the plan is acceptable to the air traffic service providers. If necessary, plans are rejected or modified. Once the plan is acceptable, it is distributed to all Air Traffic Control units (ATCU) along the route. 

In the ATCU, the FDPS will receive the flight plan and store it in its flight plan database. 

It must be noted that the FDPS is much more than just a flight plan database. It is at the heart of the air traffic control unit. It correlates flight plan data with actual radar tracks, updates flight plan with inputs from air traffic controllers and it supports local flow management functions, conflict detection systems and much more.