Example of airports connected by rail are much closer than Europe. The Cleveland RTA does much of what you describe (http://www.riderta.com/). It links to AmTrak for regional service. The Greater Cleveland Regional Transit Authority manages the regional transit system there.
The Long Island Railway connects much of New York metropolitan area to JFK Airport. It is managed by the Metropolitan Transportation Authority (MTA) which serves downstate New York and parts of Connecticut.
Existing rails link Michigan Central Depot, Dearborn, Detroit-Wayne County airport, Ann Arbor, and west to Chicago. I would guess AmTrak could extend service to-from Dearborn to Michigan Central Depot without much construction. A connection to the airport would require an additional stop and probably shuttles to get passengers to and from the terminals. This route follows I-94 and would have to compete for traffic. The train tunnel from Michigan Central Depot (under the Detroit River) only one track, but still operational and connects to the Canadian National Railway system.
Maybe the ad-hoc trails people make are natural transportation routes in your community. I think a time honored approach to such routes is to improve them, making them easier and more enjoyable to travel as well as opening them to new modes of transportation like wheel chairs and walkers.
All the transportation modes have their strengths and weaknesses.
The perception of safety often is not supported by the numbers. People who do not support mass transit may exaggerate crime to support their position. Commuter rail systems have a fatality rate comparable to cars, but the passengers are safer. Most of the fatalities are pedestrians.
I think the biggest problem with mass transit is over-investment. Often high operational and investment costs are not supported by ridership levels. Once installed, operators are incentivized to reduce operating costs by reducing service. Reduced service drives away riders in a viscous cycle.