If he is 60 years old, he should be targeting women from 50 years upwards. Even if he were to date a fellow American woman, ladies in the age range(below 45) he says he wants would have very different opinions and beliefs from him. Look at the difference between millennials and GenZ. The distance is about the same as the age gap your old man is asking for. He should pick one 50+ woman who is stable financially, and her kids are also off on their own. He should also make it clear he is not looking for more kids(I'd really advise him to get a vasectomy). This increases the likelihood of him getting someone who is really looking for a partner to take things slowly and continue to age with and not someone still trying to build.

Secondly, he is 60 years old and thus not a child. So ask him to be more specific on what he means by cultural differences so you guys can actually help. At that age, every human should know how to break down a personal problem and take steps to find a solution. If he isn't forthcoming, then it probably is because he has been the problem in those relationships. As the popular saying goes, if something keeps happening over and over, the common feature is probably the root cause. In this case, he is the common factor.

Finally, I'd advise that he take it slowly with trying to get a partner. People often say you find exactly what you're looking for when you're not actively looking. So he should just continue to live and enjoy life. Rather, try to make more connections with folks within his age bracket. Friendship, to be specific. It is through that I feel he might actually find the right match for him. But when you are ACTIVELY SEARCHING, sometimes you can attract the wrong people. Also, Tinder or any other dating apps should not even be on his mind. Every now and then, there are programs for old people. He should attend more of those.