It is going to Kansas, for Pete's sake! They can barely inspect mail incoming to the District of Columbia. As long as you are not mailing parcels to prisons or insane asylums, you are fine (they X-ray mail). You are fine, have faith in America.
How ironic would it be for the USPS to X-ray packages? As Benjamin franklin, who helped establish the forerunner of the modern USPS, said, "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." I smiled a little, thinking of this. : )
EDIT: Typo.