The whole point of a TileMap is that the tiles are batched together and treated as a single image and a single collider. This makes tilemaps much more efficient, but means you can't treat individual tiles as separate objects.
If you want to find which tiles are affected by the explosion, you'll have to find that using the explosion's position - convert it to map coordinates using
world_to_map() - and calculating the tiles that are within a certain distance of that point. You can remove a tile by setting its index to