1989 Private Pilot glider (Japan)
1992 Private Pilot ASEL (US)
1992 CFI rating on glider (Japan)
1992 Private Pilot ASEL (Japan)


You could surrender 1992 Private ASEL US, then request a private pilot
certificate with both glider and ASEL ratings based on your Japanese
license. (Presuming the Japanese licence is not itself issued on the
basis of US licence, and becomes invalid when your US licence goes).
BFR would continue to be valid. Of course if you're going to fly in the
US a lot, just doing the final few hoops for the US glider rating is
probably a better long-run solution.

John Cochrane BB