I'm American, my company is American, and all I say will apply to the USA, because that's the only place with which I'm really familiar with the laws.
A union is essential, because without a contract, the company is completely free to do whatever it wants, so long as it pays at least minimum wage (about $5.75/hour) and pays for overtime over 40 hours - unless the employees are salaried, not hourly, in which case overtime does not apply. Absolutely the only way to guarantee working conditions, health benefits, and anything else is through a union contract. The concept of a fair market for labor is asinine, because there is no such thing. The labor laws are written to favor the corporations in every case. Without a union, all workers are at the mercy of the employers, for everything. There is no safety net for health insurance or anything else. Health care is a capitalist enterprise, and thus very, very expensive. It would cost well over $600/month for just me and my wife, to continue the current coverage the company offers, which has high deductible and copays, and for which I have been paying about $240/month. There is no such thing as a right to health care; you have to pay for it, and the company can do away with all benefits with no warning. ALL BENEFITS. Only a contract prevents that.