I perplexed my US hostess when I asked if I could help lay the table

There would be no confusion at my house. And your offer would be accepted with pleasure.
Perhaps it's because NEW England was settled by the English and some phrases are still used. Although -- Hmmm -- in many homes they say "set the table" but your offer would be generally understood in New England.
Could it be I am getting old and the phrase is dropping from general use?
wow