Wow, sobering to see my parents aging. HELP !!!!

I am a 43 year old UK national who has been living in the USA for ten years. I can apply for US citizenship, yet had not done so to this point. I had not been home to the UK for 4 years ( expense ). I just got back from visiting my parents in the UK and I am shocked to see how they have aged in the last few years.

My parents are both 74. Although I was naturally concerned for there wellbeing my sister lived in the UK so I always felt at least she will be able to respond to any family emergency. Now she is relocating to Australia with her family for finacial reasons I fully understand. She is the only other direct family member.

My father is the registered care giver for my mother who has become partially emobilised through arthritis. Yet my father is showing signs of dimensia and also losing his mobility. He will put food in the oven and forget to check it and then it burns. Makes a hot drink and leaves the milk out nearly every time. Has trouble getting out of a chair, shakes when holding a drink. Has that lost look on occation. Will just sit fior hour.s He has been tested for Altzeimers ( I believe,) the test came back negative.

My father has had both hips replaced and recently his GP told him
that his hips are OK but his muscles are waisting and if he didn't exercise he would have to be lifted before very long.

My parents marriage is not the healthiest although they just celebrated their 50th Anniversary. They bicker all the time and this obviously does not aid there health. The frustrations they have of each others psychosis and ailments is very aparent.

I live in Mississippi, have negotiated my Divorce, Banctruptcy and Hurricaine Katrina all in the same year. I have a daughter who moved to Texas, 10 hours away. I am only just getting back on my feet, I am in a wonderful committed relationship, a stable job of 5 years, yet the recent experience of my sister emigrating from the UK at the same time I see the fragility of my parents alone in the UK has spiralled my new found stability into utter anxiety.

I do not want to lose all I have gained in the USA. I will not abandon my parents either.

As a permenant legal alien and green card holder I do not have the rights to bring my parents to the US or sponsor them. Unless I become nationalised. I have no problem doing that. Yet if I am able to persuade my parents to live with me in the US, I don't know how aging immigrant parents can be accomodated should they require constant medical attention in the USA.

All advise is appreciated.