New seller worried about shipping

[bradymarm]

Hi,

I am worried because the high bid of an item I am selling is to an area I thought I did not ship to.  I went to my shipping prefrences page and I had blocked out all but the united states but on my listing it says I ship to Canada and to Mexico.  What did I do wrong? Can I fix it now that there are bids? 

As you sellers know shipping is a profit killer.  I did it wrong with a pair of shoes and it almost cost me more to ship than I made. 

Thanks for your help,

Bradymarm