It is true that bankruptcy law is a federal law, and is applicable everywhere throughout the country. Bankruptcy petitions are filed in federal courts.
However, even a federal court has to have jurisdiction to accept your case. Most commonly, your case would be filed in the district and division to which your county of residence is assigned. Sometimes, you have a choice where to file if you have real estate or business in other counties, or if you spouse or affiliate has a pending case in another county.
Keep in mind that although basic bankruptcy law is the same nationwide, the way it is interpreted by local judges and trustees is not. The implications of these different interpretations are sometimes very significant – for example, you may be able to file a specific type of case in one district, but not another; you may have to pay more to creditors, or you may have to provide more supporting documentation in some bankruptcy courts. Your attorney should be familiar with practices of the court which would handle your case to provide adequate advice.