Question about insurance in USA?

So, this is purely for interests sake.  I am Canadian, but often see American women on here posting about not going to the doctor etc. due to lack of insurance.
​How much does it cost to go for a regular visit to a doctor in the US?  I am just curious, in Canada we don't have to pay.  Ever.  
​I lived in Australia, and had to pay there, and I think it was around $50 for a visit, but if something was seriously wrong and you had to go to a hospital or something, they would treat you with or without insurance.