A large wad of cash may attract questions from the Transport Security Administration at the passenger screening area, but a quick proof of ownership may be sufficient to let you off the legal hook.
Your first step is to research the currency of the country you want to visit. This will help you understand how much cash you can carry and the regulations of your destination country.
Suspicion is often the precursor to questioning. If authorities feel that you are clumsy or hiding something in your luggage, they may ask that you step aside for interrogation.