Carrying a significant amount of cash might raise queries from the TSA during passenger screening. However, promptly verifying ownership could often be enough to avoid legal complications.
There are no restrictions if you are coming in or going out of the U.S., but you must declare how much cash you are flying with to the CBP if it exceeds $10,000 in cash.
For travelers going in and out of Canada, the amount carried in cash can only equal or exceed $10000 if you have to declare to the authorities how much cash you have.
The Mexicanist reports that if the amount exceeds 30,000 USD, the penalty could range from 3 months to 6 years in prison with the forfeiture of all seized cash.
If you are traveling with excesses of a million yen, you are expected to pick up the ‘The Declaration Of Carrying of Means of Payment’ form from the customs desk.
Remember, the legality of the cash you carry does not guarantee its safety, so you must use secure ways to protect your cash against theft and fleecing.