If the reduction in hours lowered your weekly gross wage to a lesser amount than you would qualify for in unemployment benefits, then you could, while still unemployed, possibly qualify for partial unemployment benefits. The way to find out what your weekly benefit amount would be and whether or not you are qualified for benefits in your state, file an unemployment claim. If you have wages to set up a claim, even though you are still working, you will find out what your weekly benefit amount would be for the next year. And if your hours are reduced again, or you get yourself fired or laid off or let go because you raised such a stink about your three or so hours a week, then you'll have an unemployment claim already filed. The thing is, unemployment in any state is usually not as much as you could make, even working 37 hours a week, and you are only able to draw it for a maximum of six months while looking for other jobs. So it's pretty unlikely, if you're still getting 37 hours a week, that your wages are going to be less (gross, remember) than your weekly benefit amount in unemployment would be.
However, IF YOU QUIT you will very likely not be able to get approved to draw benefits! How plain can we make this? Okay, if you were working 40 hours a week and they reduced your work assignment to say, 10 hours a week, you might stand a small slight chance of being approved to draw, as this move was just a completely legal effort to get rid of you, encourage you to quit. But such a small reduction in wages, to make your wages commensurate with the other people who work there, is not illegal, is not going to be considered a valid job related reason to quit the job, and you are very possibly NOT going to qualify for unemployment benefits.
You always have the right to quit the job or to find another job that you like better, but it is not illegal or wrong for an employer to slightly reduce your hours instead of raising everyone else's hours up to what yours are. That's all there is to it, and you are 'way out of your element when you talk of complaining and whining and appealing to the big bureau of fairness that most people think is up there somewhere.