Now that you're supporting them, you have to assume somewhat of a parental or "in charge" role with them. I know this is especially hard for many immigrant families, where the culture dictates that the elders are in charge. The fact of the matter is, your life in America is largely dependent on the amount of money you have. They may be pissed if you draw boundaries, and start talking about respect and everything they did for you to guilt trip you. You control the input, but if you let someone else (who may not have the same values or long term thinking as you) control the output, you may just be shoveling water out of a sinking ship.
From their perspective, they feel like spending all the money you earn is fine because that's what their parents did to them, and their parents to them, and on up the line. The problem with that is, that will end up with your kids having to support you someday. It's also frustrating to see someone else spending your money on things you wouldn't spend it on. It's like loaning a friend money for rent one month so they don't get evicted, then seeing them post a picture of a big fancy sushi dinner downtown a week later.
You have to set boundaries. You are in charge now. Your house, your rules (or in this case, your money). They don't get to dictate the terms of how you support them. They may be used to the culture of where they came from, where the older folks call the shots no matter what, but that's not how America operates for the most part. Hinging your retirement on the next generation is risky, and in a way selfish. You're the transition generation, so it's going to be extra hard for you (and maybe your kids). You get the costs of the old system, and none of the benefits. You have to set limits on those costs.
When my girlfriend and I first started dating she mentioned someday she'd like to support her parents, since they did so for her grandparents, they're immigrants as well. She has since changed her mind after seeing them constantly spending money they don't have on stupid stuff while we live frugally. Her dad works 10 hours a week for just over minimum wage, his health is declining and he probably won't be working there 3 years from now. He just bought a brand new car for around $30,000. My girlfriend has been driving the same car since 2009, and has no plans of upgrading anytime soon. They buy giant bulk items at Costco and throw 50+% of them away, they just like buying them. The other day they gave us a huge box of granola bars because they bought it to try and he didn't like them (who buys 50 granola bars without trying them?). They're constantly buying new reusable water bottles, random DIY supplies they don't use, all sorts of stuff. Before we met, my girlfriend took them out to $200 worth of sushi about once a month when she'd visit them because she felt like it was her duty. That has stopped as well.
Her grandparents are similar. They just don't understand money very well. To them, renting is throwing money away, even if you're only living somewhere a year. They get full time care from their daughters, and refused to move with one of them to her new city if she got a rental because of how stupid they thought it was. She bought a house.