I certainly understand what you are going through; I've been dealing with this for many years now, first with my husband's parents and now with mine.
We looked into getting permits to bring my husband's parents over to live with us, but as non-EU there were significant obstacles. If one parent were left alone, and there were no close relatives in the home country, one could likely get a permit - but as both were still living, albeit incapacitated, chances were slim.
The clincher for us, though, was health care. Given their precarious health and age (mid 80s), the ILs would not be able to get anything other than basic insurance - which we felt was not sufficient for their needs. And as the ILs speak no German we worried that they would not be able to communicate their health care needs effectively. Not to mention that, at their ages, the chances of meeting other people, of becoming part of a new community, are nil.
At this stage we felt that uprooting the parents, taking them out of their comfort zone, would do more harm than good.
So we do what thousands of our generation do - juggle.
Longbyte has given some excellent advice.
Neither the ILs nor my parents wish to leave their homes, although it is becoming increasingly difficult for them to do the everyday things. We have tried to help by hiring what household services the parents will allow, and by encouraging and organizing some sensible renovations and changes. But leaving the family home is a huge emotional and psychological step - one the parents are not ready for, and one only they can decide when to take.
We have encouraged them to think about that step, to decide what they want - and do not want - to do, to be ready if and when that time comes. Both sets of parents are reluctant even to do that, as again, the emotional baggage is huge.
We have quietly done some research, made some tentative plans in the background, like getting on various waiting lists to keep options open should steps have to be taken quickly or in an emergency. I hope it does not come to that - I want the parents to decide for themselves, based on their own wishes and needs.
Aside from that, we travel back as often as possible; to juggle our family responsibilities here my husband and I rarely travel together - one goes to spend 3-4 days in the States while the other holds the fort here. We find that frequent short trips are more helpful than longer visits twice a year.
We try to have things organized here so that one of us can get back to the US within 24 hours in an emergency.
We are in contact with the various senior services organizations in the parents' towns, we hope we have immediate emergency care sufficiently organized.
We have asked our parents' neighbors to keep an eye on them - not to do anything per se, but to let us know if something seems amiss. Boxes of Sprüngli chocolate arriving periodically from Switzerland let neighbors know their help is much appreciated.
It's very very difficult. I wish I had better answers. I fear all I can offer is empathy.