Background info: I am a PhD student in Germany who is rather frustrated with his research progress. I am almost 3 years into my PhD now. My field is Theoretical Computer Science. I started working in subfield A, which is my current advisor's specialty, but gradually became more and more passionate about subfield B. Subfield B is a much more "hot" and theoretically demanding topic than A, but unfortunately there is no-one in my department who works in it (so changing advisors is not an option).
My dream is to be a researcher in subfield B. I have tried to find connections between A and B and have managed to "squeeze out" a publication that was accepted at a mid-tier conference, but I feel I am just terribly handicapped. Neither my advisor nor me have any connections in subfield B. I feel I could get to grips with the current state-of-the-art and make some contributions had I more time to do so, but my contract (as a research assistant) is only being extended for another year maximum. I get the feeling I am essentially being told to "get the thesis done and get out".
I have no real intention on further working in subfield A, so I am thinking of just throwing everything out the window and starting my PhD from scratch at a different institution. It appears almost all renowned researchers working in subfield B are in the US (with perhaps a couple exceptions in the UK), so I thought about enrolling into a PhD program there. I have a comfortable financial situation, so personally I would only really have "wasted" 3 years of my life here (but acquiring some useful experience nonetheless).
Question: How likely is it for me to be admitted to a PhD program in the US compared to I never having started my current PhD in the first place? Am I at a serious disadvantage (as, e.g., questions like this seem to imply)?
Since I studied in Germany too, I have a master's degree from there. So far, I have 4 publications in total, two of them being from my master's and bachelor's theses (one publication each). I am the single author of 3 of them, the other (about my bachelor's thesis) has my advisor as co-author. My grades are fairly good.
My fear is that my application might be frowned upon (e.g., "Why doesn't this guy just finish his PhD where he's at?") or possible advisors might be highly skeptical of me due to me "almost having a PhD" (even though I'd be willing to start from scratch).