Why try to attack, or do something yourself? Perhaps someone else, with other interests might do the job for you, if you are willing to pay a fee for it.
Hypothetically, the Panama region could be claimed back by Colombia, which in the past had ruled the region, now known as Panama, including the Canalzone. Perhaps Colombia could be bribed to take back, what had been theirs, using their large population as an Army of the masses in this conflict, which the US Forces would either have to kill (Problem of unarmed civillians getting killed), or surrender to. US troops killing seemingly unarmed civillians would be great for propaganda issues, leaving the USA with less friends worldwide, including in their own state, where the population would likely protest in one way or another.
After the hypothetical surrender of the region to the semi native population, Colombia might get in charge here, with or without a puppet government, after which allowing the Japanese and British to make demands on their terms, closing the canal for US shipping.