TL;DR: I'm reapplying to schools in the US for Fall 2021 because (1) the research project I'm getting paid to work on isn't in my area(s) of interest, (2) in general, mathematics at this university is heavily applied and computational, so there's little scope for me to do something else I'd like here, (3) I'm making much less than minimum wage (assuming a 40-hour work week for 52 weeks a year), and (4) I don't like living here. These are listed in order of importance to me. The question is, which of these points do I emphasise to an admissions committee?
More context: I'm an international student (for US and Canadian schools). I graduated with a Master's in math from a well-known university in Europe. I was "on-track" to start a PhD in Fall 2020, but due to personal reasons and global events I couldn't go to any schools in the US or Canada. I didn't want to take a year off from math, and I needed to make at least some money, so the best option seemed to be to enroll in a PhD program in Europe.
I plan to reapply to US and Canadian schools (for the reasons listed above). Only, I'm not sure how to explain that despite already being enrolled in a PhD program, I want to "transfer" to a different one. I have a solid academic record otherwise---how will this affect my application? How do I explain this in my statement of purpose?