I don't think the budget is the problem, it's where he wants to cut.
For instance, he wants to cut the size of the Army and Marines, but still wants to maintain 11 Carrier Battle Groups. We have three new Carriers under construction that will replace 3 older but probably still serviceable ones.
Do we need 11 Carrier Battle Groups? Well, let's see how other countries stack up in their number of carriers.
Italy has 2, but they are an ally
the UK Has 1, but they are an ally.
Spain has 2, but they are a joke. Also an ally.
France has 1. But it keeps surrendering.
India has 1. But we are on good terms with India.
Russia has one. China has one under contruction. Neither are anywhere near ours in terms of range, capability, etc.
So we don't need them, but we are keeping them.
Meanwhile, we are cutting the number of active divisions- again. To the point where we can't fight two land wars at once. It's an invitation to someone to say, "Well, America's Busy in Goofistan, we can launch an invasion of our neighbor."
Part of it is the thinking that the Air FOrce and Navy have to get as much as the Army gets, when the Army is the key force.