Do UK travel agents have a legal requirement to inform package holiday customers about pport requirements?

I bought a holiday package from a reputable travel agent for a Caribbean cruise with air travel via Miami. I was NOT informed that it is legally necessary in USA for travellers to USA to have a machine readable pport or a visa. I had a fully valid (non machine readable) pport and was also granted an ESTA. I was denied the right to travel by American Airlines and as a result half my family and myself had to buy new flights, get a new pport and lost a week of our cruise!