It bears repeating - in the USA a one way ticket is a flag, plain and simple. Has been that way since 9/11/2001. I do believe that as long as you can produce a return ticket to the immigration agent in Jamaica you should be fine - a one way ticket might result in some extra questions...MIGHT. The hassle won't be with Jamaican immigration. It will be with the US airports. And that will all depend on the agent you get, the airport you are flying out of - the inconsistencies regarding "homeland security" are astounding. If you are choosing to fly this way leave plenty of time before your flight is scheduled to leave just in case.