I'm guessing you are using the Canon USB webcam utility? or are using HDMI capture?
In either case, there is processing time required to convert the output (HMDI or USB) and be usable in OBS (or anything else)
A fast CPU will help... some, maybe... basic physics
After that, you'll notice a setting to delay audio (as it usually processed in a separate channel and faster).
I recommend looking up how to sync audio and video.... and not be overly concerned about an under 1 second (typically) video processing delay/lag
And such a discrepancy between audio and video processing is NOT unique to OBS. You'll have same/similar issue regardless of s/w used. To make things simple, you'd need to use a video capture device that also captures audio, and you process both as a single stream. If I recall correctly, per Canon readme/FAQ - you can't do that with their USB webcam utility