There does not mean that there is no place the budget could be cut. There is a lot of fat in the budget that could easily be cut without hurting the country at all (or hurting its most vulnerable citizens -- children, the poor, the unemployed, and the elderly). I can think of two areas right off the bat -- corporate subsidies and the huge defense budget.
The corporations receiving billions of dollars in subsidies from the government are currently making record profits and no longer need those subsidies (if they ever needed them in the first place). And cutting these subsidies would kill two birds with one stone -- being both a budget cut and a new revenue source.
And there is even more fat in the defense budget that could be cut. In fact, we could cut the defense budget in half and still be spending far more than any other country spends. And despite what the Republicans will claim, it would not hurt our ability to defend ourselves at all.
But that's not what the Republicans want. They want to increase the defense budget, and want to stop any increased revenue from corporations or the rich. They want to balance the budget completely on the backs of hurting Americans. They must not be allowed to do that!