- About $20k/y to provide health for a family, regardless of income. Median wage is barely double that amount. So most people in that situation forego health coverage (or pick the cheapest catastrophic-only coverage they can afford, and then are on the hook financially for any health issue).
- Still have 33% income tax
- Retirement: it's entirely up to you to save. Good luck! (rule of thumb is 15-20% of income)
- Child care: $12-24k/year/infant should your spouse have to work.
- College education: similar figures, maybe less with some assistance programs, maybe more if children go to prestigious schools. Or you can punt the bill to them and have them be on the hook for a loan.
- Oh, and nursing home for the elderly is about $30k/year so better get that retirement fund full of money. Though it's an undue burden to place on someone else, the traditional view is that having children can help reduce that cost.
In short, the US' system is not optimized for the median citizen ($59k in 2016), it's optimized for those who are in the 75th percentile or above.