Mona Pereth wrote:
Which specific cities and/or countries do you recommend
The answer is different for different people with different personalities and preferences. For example, your message mentions NYC, and I remember multiple comments about NYC from different people, and roughly half said NYC is good for meeting people, and the other half said NYC is bad for meeting people. Although these people say the opposite of each other, I believe they're all correct because each of them is saying what is true about NYC for himself/herself personally.
If I'm asked to make a location recommendation for only autistic people and no other types of people, then this might or might not be possible to do, but in any event, the necessary statistics are missing, and nobody is willing to fund a study to collect statistics about which cities and countries produce the highest rates of success for autistic people.
I suggest looking for a "no lose" location to try. A "no lose" location is one where even if you discover that it's the wrong place for finding a relationship partner, you won't have lost anything because it's overall better than your previous location, so you still end up making a gain in one way or the other.
And then, to improve your chances further, search for a relationship partner in the chosen cities or country BEFORE you move there. Some people will reply to you, "I would be interested in you except I'm not interested in a long-distance relationship, and I'm especially not interested in anybody who keeps saying 'I'll move there soon', but never actually does it."
Then ideally you're already prepared in advance, and you're able to honestly reply, "I think the same as you. I'm actually already willing and able to move there within the next 3-4 months."