Nothing about fissile material in there either. It is self evident by the context. If we have the right and duty under our constitution to prevent the smuggling of fissile material into our nation, then we likewise have the right to prevent the smuggling of any other material which may be used to kill or injure Americans.
Do we have the right and duty to prevent people from smuggling fissile material? Or Biological Weapons? Or Nerve Agents?
Federal authority to exercise control over goods coming across our border from foreign countries is well within the original intent of the Commerce Clause. This is commerce "with foreign nations", not interstate commerce. The were specified separately because "with" and "among" mean different things, and were intended to be treated differently. If it was all intended to be treated the same, they would simply have said "to regulate commerce" and left it at that.