Question is, 'Can they do this?' Answer is yes. In the absence of a union or a contract of some kind, they certainly can. Can they do it legally? Well, if you want to, after they've done it to you, file a complaint with the EEOC and let them take a look at the situation. The question is, as you say, they are trying to "chase you out of here," and you speak as if they are chasing out a fair number of people besides you. Who are these people? Is it people that are older, green people, left handed Moravians? If it is those of a protected class, that's much more likely to seem like illegal discrimination to the EEOC when they investigate. I have also seen illegal discrimination called in a case where the people who were former employees of a company that had been bought out were being targeted for dismissal, and it was because these employees tended to be older workers.
But continue to do the job you are doing to the best of your abilities. DO NOT QUIT THIS JOB unless you have found another very good job to replace it. Let them fire you if they want to do this. In many cases, companies think they are being clever when they do this sort of thing, without considering the repercussions. Whoever thought of this is pretty much an idiot. They could give you a "lack of work" separation notice and have you out without taking any sort of risk of doing a thing that is discriminatory or illegal if they want to get rid of you so badly.
Either way, as soon as you are given this separation because you no longer qualify for the job you have been doing for two years because they changed the job description, file immediately for unemployment insurance benefits. You will not be terminated for a valid job related misconduct reason, and your chances of being approved for benefits, even though you have been terminated, are excellent. Then immediately, contact the EEOC and file a claim about the possible discrimination involved. The two things, EEOC complaints and unemployment benefits are not related, and you'll need to do both. EEOC issues usually take a while to resolve, and unemployment benefits are a much more immediate source of assistance.