Sad thought.
We know scripture tells us we wrestle not against flesh and blood. Fact is, I don't see any wrestling taking place in the church at all.
That isn't true of every church, thank God, but sadly, of the majority of churches in the west.
Scripture also tells us in Revelation that satan will be bound for a thousand years, so that he would not deceive the nations anymore-Rev 20v3.
The nations are deceived, fighting a losing battle against God.
Whether the church would notice or not is questionable.
I think the world would notice, and claim the credit for themselves.
As for if we would notice if the Holy Spirit were present or not during a service, not a chance. We would not notice. We don't notice now, we are too entertained to notice.
I believe it was Leonard Ravenhill who said
entertainment was the devil's substitute for joy.
It's also satan's substitute for the Holy Spirit.
God bless.