I'm not making the simplistic argument that I'm glad that the government protects me from gangs. The gang example is illustrative of a deeper point.
The government's institution of property rights, which are protected by the police, army, courts, etc, makes everything around us possible. Without that basic order, there is no wealth creation. In the state of nature, a skinny nerd like Mark Zuckerberg is not king. In the state of nature, the kings are the people in the gangs: young, strong, capable of using and organizing force. I don't believe in a god that says "thou shalt not steal" or "thou shalt not kill." I have to depend on a utilitarian justification for the existence of property rights: that they allow the existence of the kind of complex society necessary to create wealth.
The imposition of this wealth-creating order is not free, and the cost is not just what we spend enforcing order. The cost is enormous: taking away the only natural ability common to all people: taking what you need. When we create property rights that allow a landowner to own vastly more land than he could personally defend, we take away the ability of people to hunt and fish and subsist on that land as they would in nature.
I believe that programs like welfare, food stamps, etc, are the moral obligation concomitant with the imposition of this highly artificial order. The order exists because it results in the greatest good for the greatest number, but in the process it creates a class of losers. I believe we have an obligation to take care of, as we can, the losers created by our order. I consider such expenditures to be a cost of creating that order that ultimately makes my income possible.
You don't have to agree with me. I think it's immoral to impose an order that prevents people from fending for themselves outside that order, and then to not provide for them. You may disagree with that.
Beyond that, even if you disagree with that premise, line item thinking is still nonsensical. For example, take the spending on Medicare and social security. You can disagree with whether national insurance is the most economically efficient way to take care of the elderly, but the cost wouldn't disappear if we got rid of those systems. Instead, the elderly would move back in with their kids, as they have done through human history. The cost to you is not the cost of the program, but the cost of the program minus the cost of taking care of your parents yourself. This is generally true for every line item--you have to engage in an alternatives analysis instead of chalking up the whole dollar value as not benefitting you.
Moreover, in many situations the cost to provide a service would be much higher without the government. For example, consider the 15% of all spending that goes to education. Our modern society would not be possible without this education, and employers benefit from it tremendously (what is the incremental benefit to an employer of someone who can't read versus someone with a public education?) People act like education is something that benefits individuals, but at the end of the day, an individual only benefits from his own education. An employer benefits from the education of each of his employees. And due to the public good nature of education, it's unlikely employers could provide it more cheaply than the government.
In general, I find the approach of "look how much we spend on X" to be intellectually lazy. Nearly every $1 you spend on taxes benefits you in some way. The debate is not about whether it does, but how much it does relative to that $1 and whether there are alternatives that cost less than $1.