@ pdq - "

Just for the record, Mexico requires that all visitors carry papers and show them if asked.

Federal law in the US probably requires the same, but we do not enforce such laws."

The US may technically require that of all visitors -- I don't know, but when I lived in Canada I was not required to carry my passport or proof of landed immigrant status with me. But we do not require that citizens carry such proof when travelling within the US.

Mexico probably does not require their citizens to do so either.

It's not only damned inconvenient to carry such documents on your person at all times, but it poses great risk of loss or theft of those important proofs of identity and legal status.