There is no legal restriction of how much money you can carry around with you in the US, I believe. When you cross a national border you need to declare it and if you buy casino chips or deposit into a bank, they will report you to the government. But the cops can and often do "arrest" the money and will take much smaller amounts of money from you if they find it.
The limit is not 10,000. There may be an official number where that starts happening but I have seen it happen (completely anecdotal) with amounts as low as $800.
