It is far from 10-20x difference. And many or most of those nations have stronger worker protections than the US, calling into question the idea that labor law is really the main driving force there. It's probably more like propertyholder protectionism (i.e. NIMBYism) dominating local politics.
Those nations also have stronger social safety nets, including health and retirement benefits provided nationally rather than by the employer. Your first article mentions that operating costs per ride in the NYC metro are $4.11, compared to $2.61 in London. It also estimates though that $1 of that is health and retirement benefits.
Helsinki is currently building a metro expansion for $103 million per kilometer, at least if I got the numbers right. Of course the setting is very different in New York vs. outskirts of Helsinki, but yes, it's cheaper.
With all our modern technology, we should be able to achieve what our ancestors did. Even with our higher standards for safety.