You need to convert the footage before you import, H264 does not work well with FCP. Use Log and Transfer but ppoint it at the folder containing the clips, not the actual clips. If it doesn't work use Mpeg streamclip to convert to Pro res then import.
You are trying to use the camera's native H264 footage which FCP does not work with well at all.
There are Log and Transfer plugins that you can get from Canon to make it work or you could use Compressor to transcode to ProRes LT before importing.
There's an important advantage to installing the canon plug in and using log and transfer. If you've properly placed the card contents in a folder with a unique name, fcp will assign this name as a reel number for the clips and if you need to relog and transfer this material, you can do it without any issues. In this example EF8_28_13DSLR Chip1 becomes the reel number for any clips from this folder.