Huh? I'm asking about the realistic outcome, whether that be denial of border crossing, criminal charges, or they choose to not examine the device and let you through.

now what if you bought the phone off craigslist?

That's likely not relevant since during a border crossing your identity has already been verified.

"how was i supposed to know the phone i bought on craigslist had a payload?"

plausible deniability.

edit: please dont actually do this.