The US Budget is a complicated, multi-step process. The foundation is the President's budget request, but Congress has multiple authoriztion and appropriation votes plus the House-Senate reconciliation on each budget item. The legislators really have, and exercise, absolute power on the budget. Frequently they do really stupid things, false economies, in order to fund their own pet projects and initiatives. Often they zero a presidential item, or resurrect one the president has killed, sometimes for nothing but political reasons, sometimes because the administration is either playing politics with his requests or because of embedded bureaucratic inertia keeping moribund programs going.
A smart president with an effective administration will carefully design his budget to get through Congress with minimal change and disruption of his plans. This doesn't happen too often and Congress has become very adept at designing its own budget.
If you are managing a government program the best you can hope for is to get your numbers for apprpriations in the president's budget, past OMB and all the executives between you and them, and then have Congress pretty much ignore the details and rubber stamp it. Not likely to happen if some Senator is on the hunt for the money to build a bridge or school with his name on it while keeping the overall budget within the limits Congress has imposed on itself.
So if you want to blame anyone for the increase in spending, blame Congress, and mostly blame the people who elect them. By the time they get done the President has little say in how much or little he can spend or on moving money around between competing programs, and Congress has even extended its legal control into managing DOD procurement programs. I personally know several people, USN officers and high grade civilians, who were fired or demoted for moving excessive money between components of the F-18 program in violation of the appropriation bill.
Wikipedia:
The President's budget request
The budget begins in February with the submission of the President's budget request. According to the act, the budget request is submitted to the Congress on the first Monday in February. At this stage, the budget request is not binding but merely constitutes an extensive proposal of the administration's intended spending for the following fiscal year. The budget proposal includes volumes of supporting information intended to persuade Congress of the necessity and value of the budget provisions. Funding requests for all federal independent agencies and cabinet departments are included in the President's budget request, and each agency and department provides additional detail and supporting documentation to Congress on its own funding requests.
Budget resolution
The next step is the drafting of a budget resolution. The resolution is drafted concurrently by the House and the Senate budget committees. Following the traditional calendar, by early April both committees finalize their drafts and submit it to the respective floors for consideration and adoption.
Once both houses pass the resolution, a conference report is drafted by members of the Senate and the House. The purpose of the conference report is to reconcile any differences that may exist between the House and the Senate versions. Usually, the conference report is adopted finalizing the budget resolution.
In contrast to most legislation passed by Congress, the budget resolution is a concurrent resolution and thus does not become law and does not require the signature of the President. As a result, no money has actually been appropriated at that point. The budget resolution then serves as a blueprint for the actual appropriation process. The fiscal year begins on October 1st.
Under the U.S. Presidential system, the support of the Congress for his appropriation requests is not necessary for the separately-elected President to remain in office, but can severely limit his ability to govern effectively.
In the United States, two types of legislation are used to spend money. An authorization establishes a program that will later spend the money, but may not provide any funding. A mandatory program is one that does not need an additional piece of legislation known as an appropriation in order for spending to occur. The authority for spending to occur for the mandatory program is included in the authorization legislation. Social security benefits are an example of a "mandatory" program. An authorization can create programs and make known the intent of the United States Congress about the level of spending for programs that also require an appropriation. What distinguishes a mandatory program from a discretionary program is that after Congress enacts a law creating a mandatory program, the program is permitted to spend funds until the program expires based on a provision in law, or until a subsequent law either terminates the program or reauthorizes it. "Discretionary" programs typically require annual appropriations legislation.
An appropriation bill is used to actually provide money to "discretionary" programs. Appropriations are generally done on an annual basis, although multi-year appropriations are occasionally passed. According to the United States Constitution (Article I, Section 8, clause 12), military appropriations cannot be for more than two years at a time. An annual appropriation requires that the funds appropriated be obligated (spent) by the end of the fiscal year of the appropriation. Once the fiscal year ends, no more money can be spent via the prior year's appropriation. A new appropriation for the new fiscal year must be passed in order for continued spending to occur, or passage of a special appropriations bill known as a continuing resolution, which generally permits continued spending for a short period of time--usually at prior year levels. The Anti-Deficiency Act makes any attempt to spend money for which there is no current appropriation void.
According to the United States Constitution (Article I, Section 7, clause 1), all bills relating to revenue, generally tax bills, must originate in the House of Representatives, consistent with the Westminster system requiring all money bills to originate in the lower house. The Constitution also states that the "Senate may propose or concur with Amendments as on other Bills," so in practice the Senate and House traditionally proceed separately, with each body drafting and considering their own bills separately. The Senate generally will amend its version of a particular appropriations bill to the House-passed version in order to send the bill to a conference committee prior to the bill becoming law. This is why the majority of appropriations bills that are enacted contain the H.R. modifier used to identify House introduced legislation.