Who is responsible for credit card debt if your spouse dies and the credit card is in his name only and husband leaves everything to his son?

The "estate" of the deceased, including assets and debts are filed in Probate Court. If there is a will, that also enters into the filing. The way it is distributed is dependent on the state of residency governing statutes. In some states the estate needs to exceed a specified amount, before a filing is required. Most states allow the surviving spouse, to keep the majority of assets, including the homestead. Under, of course, the provisions of the secured lending contract,(mortgage), if that applies. Whatever is not exempted and/or distributed by law to the surviving spouse is used to pay off outstanding debts. If there are no attacheable assets, the debt in this situation is not collectable.