There is bound to be corruption in government, for mainly two reasons that I can see (just my opinion here).
The first has to do with fallen human nature. And the second has to do with the issue of our country not ever officially adopting the Catholic stance of the Social Reign of Christ the King.
The non-Catholic founding fathers of this country presumably wanted a place where men are free to make their own way - self determination, and I think that religion falls into that category as well. They seemed to think that if men are free to determine what is true or not, that they would make the right decisions, and do the right thing. They didn't take into account original sin. We need Truth to guide us so that we can make the right moral decisions. If truth is relative, which freedom of religion encourages, then really there is no such thing as absolute truth.
But we as Catholics do believe that there is such thing as absolute truth. The Apostles were told by Our Lord to go out and convert all nations. He said "nations."
We see now how the methodology of the non-Catholic founding fathers was wrong.
Also, unbridled capitalism (an form of Marxism, IMO) leads to the servile state, as Hilaire Belloc wrote, where corporations rule, and private ownership of business and property decreases). That has created a lot of problems, too.