I suspect it is trivial for the US to check who boarded flights across the world, and you left many other digital footprints (payments, cell phone activation, e

I suspect it is trivial for the US to check who boarded flights across the world, and you left many other digital footprints (payments, cell phone activation, etc). IANAL but I believe that lying to immigration when entering the US is a pretty efficient way to get banned from entering for life.