When an Invader with Strife is not participating in Ravage, is the Strife also ignored for modifiers to Ravage Actions?

No, the Strife still counts as being in the land for Ravage Actions unless some effect is explicitly ignoring Strife.

In particular:

The Fear Card "Beset by Many Troubles" still grants Defend based on that Strife;
The Event "Stricken" still skips the Ravage Action in that land;
The Event "Cooperation Among Towns" doesn't grant bonus Damage if any Towns/Cities are still participating in that Ravage;
Dahan in that land don't participate in Ravage if they're near the Incarna of Wandering Voice Keens Delirium (though this is also true for other reasons)