I started to work for this convenient store last month for $2000 a month plus some cash. I get my salary every 2 weeks. It seems like I've been paying too much of taxes. Of $1000 paycheck, I get $853. Is this normal? What might my employer doing wrong? Can taxes be $294 for $2000 earned?

Did you work last year and did you get w-2? If you get w-2 you will know the math.
If you have not got W-2 then the difference will go to his pocket.

My paychecks aren't any different than yours, and from this year, about 20% of my gross income goes into taxes because now I have to pay social security and medicare taxes on top of federal income tax. Thank goodness, Texas doesn't charge state income tax!
You're paying a lot less than many are, so stop complaining and get back to work. Like others have said - if you're paying more than you should be, you'll get it back when you file your taxes.