I would imagine that if you didn't have insurance, you would go without medical care, since it is prohibitively expensive here in the US. Having said that, if you show up at an emergency room, they are required to treat you. Whether you can pay the bill or not is another story.

My insurance covers everything, but I am paying a portion of the premium (deducted from my paycheck), as well as a portion of the bill when I'm treated (it's a $30 flat rate called a copay for a general practitioner, or $50 for a specialist). The breakdown is different for in-hospital stays, where you may be paying a percentage of the final bill (20% or something like that). In-hospital stays are usually in the thousands, but they try their hardest to kick you out at the end of 3 days. They told my mom they were going to put her in a wheelchair in the lobby after her surgery because they needed the bed. Fortunately, I got to the hospital in time.