This sounds similar to a scenario from my career, so I understand the frustration and the concerns you have. Anytime there are M&As there are significant change events at work. Often people get moved around, and sometimes they get screwed in the process.
If management hasn't cut any jobs yet, make sure you are prepared for that possibility. It may not happen now, but at some point, when processes are streamlined, and teams are integrated, executives think it’s time to have fewer workers. So, develop a job search strategy, update your resume, and post it on select job boards, even if you have been told no layoffs are planned. Some companies can hide behind the word “layoffs” by doing small, staggered reductions in headcount, so they do not have to report it.
Should you talk to an attorney? That is always an option, however, you are employed in an at will state meaning you can be terminated at any time for any reason without notice. In addition, your job description may have an “and other duties as assigned” clause in it, meaning you can be tasked to perform other tasks. The bottom line is if you want to keep this job, you have to perform the role they assigned you, or convince them otherwise.
I only have a glimpse into your situation, but I suggest you voice your concerns again, but do it alone. It’s admirable that you want to help your peers, but focus on yourself. Talk to your manager or the same person(s) you were told to report your concerns to originally, or if you feel comfortable going up the chain, have at it. Here’s how to approach the situation:
Request a meeting, stating you need some help with a work situation.
Prepare your talking points for the meeting in advance. Have a strong opening stating and show appreciation for the meeting. Mention that you want to talk about your new role. State why you are concerned about the new role, your lack of experience and any other concerns you have about the change,
Rather than focusing on how this impacts you or the team, focus on what you’re suggesting is in the best interest of the company. By doing so, you’re likely to get less resistance and get somewhere. State that you feel unprepared to handle the new role, and that you’re concerned that switching to the new group may create some problems for the company since this is not your area of expertise. Is it a liability issue? I'm not sure, but you should know.
Share some specific examples to highlight the potential impact on the company.
Ask, what can be done and/or whether it’s possible for you to return to your prior role.
If the answer is no, ask for training so you can perform your new role properly.
What you are experiencing frequently happens during M&As. That doesn't make it right, just makes it a reality. Be assertive in attempting to facilitate the change you want. While you’re doing that, go ahead and update your resume, start networking and try to get another job. Layoffs, firings and re-organizations are common activities that often don’t seem logical. It’s best to protect yourself and have options.