What is the difference between it usually takes a really long time until I can fall asleep
and it usually takes a really long time for me to fall asleep ?Feel free to just provide example sentences.

There's a difference in emphasis between the two sentences.

- "It usually takes a really long time until I can fall asleep": places more emphasis on the length of time that it takes to fall asleep.

- "It usually takes a really long time for me to fall asleep": places more emphasis on the subject, "me," and their difficulty falling asleep.

The first sentence emphasizes the duration of the time it takes to fall asleep, it's a statement of fact, without much emphasis on the person's feelings or emotions.

The second sentence emphasizes the personal experience of the subject, it's a more personal statement, it implies that the person is struggling to fall asleep and it highlights the difficulty of the process.

Both sentences convey the same idea, but the second sentence is a more natural and idiomatic way of expressing the subject's experience and it gives more context about the person's struggles with falling asleep.