Game? Sure, if you’re willing to spend a non trivial amount of time integrating with a graphics API, but that’s true of most non C++ languages. Kernel? Probably not, AFAIK there’s no subset of Julia that can run without an OS (like for rust and C++).

To me it seems obvious that you can write any application using any Turin-complete language. So the question seems more like "how convenient would it be to write a kernel or a game using Julia and with which performance impact?"

For games, it will highly depends what kind of game, of course. Assuming cutting-edge 3d-graphic intensive video-game, it will be probably not be your language of choice, especially regarding available out of the box libraries. For implementing Tetris, I guess you make it in any language for sufficient performance. :)