Can we get our L2 visa extension outside home country

My son is a student in Canada on a study permit, we need to get his L2 visa extension stamped. Can he do it from Canada or does he need to visit his home country India.

If he already have L-2 visa stamped in the passport, then it should be ok to appear in CA for this.

However, US consulates in CA are pushing away TCNs (Third Country Nationals) due to huge workload. So it would be better to check w/ the consulate first and then appear for stamping.