At US airports, a GE card is not required by CBP to use GE during the six month grace period after the card’s printed expiration date. Whether or not the GE card is expired, you can still use GE to enter the US at US airports of entry during the six month grace period after the GE expiration date.

I can’t speak to trying to use the expired card in that grace period at US land ports of entry, but I can speak to its use at airports from experience.

At US airports, the TSA has accepted expired ID as ID from me for up to a year after the card’s expiration date; but in such situations they have also asked me if I can show other ID that hasn’t yet expired (which I do show if it’s readily available on person). But when showing TSA a PreCheck boarding pass with an expired GE card as ID, in my experience the TSA have been more insistent that they be shown currently valid ID. I’m not sure if the TSA policy for PreCheck boarding pass holders with recently expired ID is to refuse PreCheck screening to such travelers without currently valid (unexpired) ID to present, but presenting other ID that is currently valid (along with a PreCheck boarding pass) works to still get PreCheck screening at applicable airports even when the expired GE card and flying in the six month grace period.

At Canadian airports, CATSA has refused to let me use the fast track security screening lanes with my expired GE card, but I have way less recent experience with that than I do at US airports.