The virus is made of RNA. Whether it is infectious or not isn't related to whether RNA is found - it's the state that the RNA is in, as I understand it.
If the RNA has been broken into pieces, it's not infectious (and this can happen immediately upon collision with a surface 0r the virions can float gently onto some surfaces and remain viable for...quite some time, usually said to be 72 hours).
Broken up bits of RNA are not viable. It is still easily determined that the bits belong to Coronavirus - but they are not infectious.
I agree with you that it's highly unlikely that someone would be infected by CV either by touch (on most surfaces, after a few hours) or by virions still floating around after a few coughs hours before.
However, the big threat is breathing in an enclosed space. In a space the size of the average bedroom, an adut will continue to breathe out live virions if they are infected and those virions will mount in number creating the potential for a very high viral load in that space. Same for hospital rooms.
At a house party, in a place with a positivity rate of 10% (there are places with much higher positivity rates in the US), then if there are 200 people, 20 of them will breathe out about 100,000 virions in normal breathing, more if talking or laughing. So even if the whole house is used for the party, if there's not good ventilation (and there rarely is - the air needs to exchange 4-5X per hour to get close to keeping this event non-infectious), within an hour, the entire place is center of contagion. Nearly everyone will be exposed, many will become transmitters (and many of them will be asymptomatic).
Churches, obviously, fall into the same category as a house party (and may be even less well ventilated than some homes, depending on the church). How long does the air remain infectious? No one knows. Would I want to go into that space after only 4-5 hours? No way. It's possible that in frequently used spaces (like churches), the waves of infectiousness overlap and are fairly continuous (which is why we see 100 people in a congregation infected after 1-2 events).
Would there still be live virions in that space (if it was not occupied for 3 days)? Probably a few. If a person's immune system wasn't at optimum, yep, they could still get Covid. For example, someone with the flu is thought to be way more susceptible to acquiring Covid in this manner, although we won't know for sure until flu season is more under way.