could the US government improve the budget through self-funding methods?

There are many self-funded or partially self-funded government entities. Those include the post office, many pension funds, the Federal Reserve, and many others. Many of the bailouts were started with a cash of government money but then used self-funding methods to return most of it, like the auto bailout or the bank bailout.

Couldn't the government start and then build similar programs where the goal is not just to use fundraising methods to reduce costs of expensive programs (like pensions) but to actually earn revenue that could offset debts and deficits?

The government already provides grants and direct spending, getting little or nothing back, on infrastructure, which improves the whole economy over time. Why not use some of that money on loans instead of grants. Essentially, the government would be improving the economy in the exact same way that private sector actors do. The government would focus mainly on areas of high risk that are underfunded by private investment but important to the future, such as green energy, transportation, space exploration, communications technology and standardization, etc.

As some examples, the US government could offer loans to struggling rail companies seeking to build new high speed lines. In 10 years time, they could pay those loans off several times over while providing cleaner, safer, and more convenient transportation between the most heavily trafficked routes, freeing up air travel for where it is used best, for small city travel.

Another use would be for foreign and international relations policy. Micro-lending programs have been among the most impactful charities, dollar for dollar, of any on the planet. They usually make money while improving lives and spreading good will to the people. The US should get in on that, shifting some of our foreign aid money into those types of programs where we can generate good will toward the US, build up peaceful middle class societies that can act as a check to make sure foreign governments are democratic, and achieve many of the same goals that the foreign aid money we spend now already achieves. And it could be self-funded or nearly so. On top of micro-lending the US could invest in foreign companies with built-in conditions that other entities won't impose, such as fair labor conditions and environmental protections that will help level the playing field with the obligations of American companies so we can compete fairly. We can also, to the extent possible with our international treaty obligations, favor US companies in that investment, boosting the American economy while other investors seek out countries where they can prey on cheap labor.

What do you think? Am I missing something in my analysis? It would take a while to build up a program like this, as you wouldn't want to spend too much getting it started, mostly shifting money from other forms of government spending, but it would provide a lot of benefit in the end and once it's running, it would offset rather than increase the tax burden.