Lightroom LRC crops imported CR3 Images

If you have set a crop ratio in the camera which is not the default (usually 3:2 in Canon cameras), LrC will apply that same crop to the Raw file on import, but retains the original aspect ratio should you want to restore it. To do that, open the crop tool in the Develop module and you should see the whole 3:2 image is available, with the in-camera crop ratio overlaid. To restore the original image ratio, click on the Reset button in the Crop tool panel.

Nothing can be done with the Jpeg image, as the crop will have been baked in by the camera when the Jpeg was created.

To stop both of those things happening, check what aspect ratio you have applied in the camera's settings and restore to default if that's what you want.

If that's not the problem, check to see if you have applied a develop preset during import which applies a crop.