With questions like this, we have to decide whether to answer the question literally, as if it could be taken literally and as if it was written by a professional (who wouldn't actually even need to ask) ... or to try to alleviate the general confusion that might be behind the text written in the "question" field. I choose the latter approach.
Quote from https://en.wikipedia.org/wiki/Borrowed_chord
Borrowed chords are distinguished from modulation by being brief
enough that the tonic is not lost or displaced,
Are you able to figure out where you feel the tonic to be? Can you verify and test your feelings - "now I sense the tonic to be here, and I can prove that to myself by playing or singing such-and-such notes?" Do you know what to play in order to establish a tonic in your mind? If not, those are essential pieces of musical skill and know-how, and you should get them in order as a first priority, if you want to learn to handle, or talk about handling harmony.
If you cannot sense where your subjective tonic i.e. harmonic center of balance is, and whether playing a series of notes or chords moves your feeling of tonic or not, then you need to develop that skill first. Otherwise you have no idea what the text is talking about when it says "tonic" - and tonic is an essential concept when talking about borrowed chords.
Sensing the tonic is about skills and practice, not about knowledge and calculations. What counts is how you feel when you hear the music. Not what you're able to place in some math formula on paper.
I tried listening to your chord progression: C#m - Am/C - Em - D#m. Assuming that I let the first C#m chord to establish a tonic in my mind, then I could plausibly think of the second chord Am/C as having been "borrowed". It mixes up the feeling of notes around the tonic, but without confusing my sense of tonic. Or actually, it makes me expect that this tune might end up going to E major at some point, but that's ok, because I consider relative major and minor keys as two sides of a bi-polar "key". I don't consider a shift of balance between C# minor and E major as a modulation, not in the kind of music I play anyway.
But then the Em chord ... here it makes me lose track of C# minor or E major being a home chord. So I say it's not a borrowed chord for me, and I don't have to justify that statement with any sort of "what notes are there in some scale" math. My ear just can't modal-mix a minor triad on a major tonic, and keep a sense of the original major tonic. The other way around it does work and is regularly done in minor keys - in C# minor it's customary to modal-mix in a C# major chord e.g. when going to an F#m chord. And the C# would be called a "secondary dominant".
And the final chord D#m, it's so far out, whatever remaining sense of tonic there was after the Am - Em combination, is completely out the window now. If you had placed the D#m directly after a C#m tonic, then I might consider it as a bit of modal mixture, bringing a C# Dorian feeling, if I had been assuming some other modal feeling. But all in all, the way you put the pieces together, the only brief moment of borrowing feeling was the Am chord.
However, if I only take the first two chords, I could continue the progression towards a final E major like so:
C#m - Am/C - E/B - Am - E/G# - Am6/F# - E.
Now it's quite nicely in E major, but every other chord (in italics) mixes in things from E minor. And there's a descending bass line which makes it a bit nicer. And the chords in italics could be said to have been borrowed. The important thing is not to lose your sense tonic. Or, what do I know, maybe you don't feel the E as a tonic there?