Hi there,
You have 2 problems.
1st - cruise line industry shy away from employing US citizen, because they tend to be very aware of their rights, respond loudly to unpaid overtime, lack of sleep, high stress and low comfort level.
2nd - if you're above 35 years of age, you physically fall behind what's required from you, no matter how prepared you are. Now imagine a 20 years old Indian as your boss, outperforming you at most levels ... asking you to do hundred things you're not used to, cleaning ceiling for example, washing drains .. and so on.
You might succeed, in spite all, but I don't recommend. It is not uncommon at all to see girls from all over the world bar tending on cruise ships, there is constant demand for them, some agencies are looking for female bartenders only, but very few cruise lines are willing to employ US citizen. Disney Cruise Line perhaps ...
Don't be fulled by "equal opportunity employer" statements on their websites. In 99% cases, they put it there only because makes them look good.