Detroit is interesting because unions played a major part in destroying its car industry. At a time where US car companies badly needed to adapt to the new Asian competition, most of their money was spent paying for pension and benefits of people who had left the workforce years or even decades earlier. So they entered the death spiral of downsizing, outsourcing and such.
Same thing happens with civil servants and public workers in many cities in North America. Not only are the services severely downsized (such as in Chicago where they had to reduce the school calendar to be able to afford the gold-plated teachers conditions), but in many cases the cities have to spend tax money on pension and healthcare of retired employees who did not work harder than current ones, but simply happened to be in the workforce when the economy was booming and the unions had the cities by the balls. The result is that people who can't themselves afford a pension plan or decent healthcare and who will live in poverty when they retire have to pay for those lottery winners.
Another issue with unions is the lack of flexibility. They hold onto job descriptions to a point where it becomes totally absurd. Such as in the case of those people working in one of Warren Buffet's newspapers (I think the one in Buffalo); when the newspaper brought in a new machine to fold papers, they couldn't change the job of those poor union workers who used to fold newspapers manually. So until they retire, those people stand in line besides the conveyor belt where the newspapers exit the folding machine and in the air they make a move with their hand that is similar to what they used to do to fold the newspapers manually. They are known as "the blessers", and they are the perfect example of a situation where employees become wards of the company, not part of a team that is there to help the business.