I've tried to do it but still not working. It seems to me this error is raising because KTUtil is not imported on KTCard. Import both together didn't make it work.
If you need any further help please let us know your Keen version and the code you used to include the core components and import. Are you using Keen's default webpack build method or creating your own? The default webpack build should work fine if you just follow the documentation. If you are rebuilding Keen with modular core components then this will need major changes in the code since at the moment the modular js is not supported.