Keeping your mailing address current in the FCC ULS database is critical!
The FCC does not mail much to you but if a letter from the FCC is returned the FCC can and will IMMEDIATELY TERMINATE YOUR LICENSE! It is critical that you make sure to forward your mail and update the ULS database ASAP. You can update your contact information online. For instructions on how to update your license information please visit the FCC web page https://www.fcc.gov/wireless/support/common-amateur-filing-tasks/common-amateur-filing-task-changing-address
The FCC uses your mailing address to determine your possible callsigns. If you want a callsign outside the continental US then you need to insure that your mailing address is in the area assigned for that callsign. This also means there must be a Post Office in that area. There are a few islands that have reserved callsigns but no Post Office. In order to get a callsign in that area you must request special permission from the FCC to have that callsign allocated to you. This is generally reserved for DXpeditions to those islands and usually not available for individual callsigns.