First to protect us against other governments that wish to take us over.
Second to help direct money to systems that will increase the wealth and stability of the nation.
And third to help protect citizens from the actions of other citizens.
I think that pretty much covers it from my point of view.
1. I think our government tends to overexert force here. We should not be fighting all these wars to protect other nations, unless it is a way to help us out. Fighting other governments (like Iraq) should be what it is capped at. Fighting bands of other government citizens should not be the case.
2. Things like roads, internet, scientific development and a lot of other government programs that have spurred on innovation have made us as powerful as we are today. Also by not allowing things like the banks to fail means most of peoples money was not destroyed during what would otherwise have been busts. We have busts, but they are generally not as devastating today, unlike before when they government took the classical stance of allowing things to just spiral out of control and fully collapse before it eventually came back around.
A recession can be caused by a lot of different things, but it in essence comes down to people and businesses stopping their spending. To keep the system rolling this is when the government should and does step in to make up for that loss in demand, and increase it's spending (like the stimulus package) to stop the bleeding.
But what it forgets to do (except Clinton) is to build a surplus by raising taxes a bit (to curb too much fast growth) and cut government spending, when things are running well, so that they can switch to lower taxes and more spending when it is needed.
And too many govern with emotion, not knowing the consequences of their actions if they do things like rent control.
3. Stopping crime has moved into a realm that they feel they need to protect us from ourselves, and that is too far. I have no problem if they are arresting people that are about to commit a crime against another citizen, but to decide that a woman cannot have an abortion, that you cannot do drugs, banning books in school, arresting musicians for lude acts on stage, banning sexual acts, banning gay people from getting married, on and on is infringing.