Is healthcare in the states really as bad as people say?

I'm talking about the cost of it and likelihood of approvals from insurance companies, everyone always says people go broke because of it. My wife is American, we live in Canada (have 3 kids) and are considering moving to the states but the main thing holding us back is fear of their healthcare system. She's a nurse so she would have a job with insurance but even with insurance, do they always find a way to deny you?

Edit: I didn't realize this post would become so popular lol thank you everyone for the replies. For the people saying how much hospitals stays cost them, would you be able to say if you have insurance or not? Or if your insurance was declined for whatever lame reason? Thank you!