McConnell and Ryan refuse to consider bills unless 50% of their party supports it. This essentially prevents any bipartisan deal on issues such as immigration.
Polls have indicated that the DREAM Act is supported by an overwhelming majority[0]. If representatives don't mirror that support, then the problem is with them, not the bill.
You are right! But also, the problem is that in red states, Republicans have managed to gerrymander the crap out of their districts to ensure they won't get unseated no matter how badly they represent their constituents.