"/i/If there are 30 red states capable of producing 60 GOP senators/i/"
"Because there are not 30 red states. There are maybe 20 with the rest like Ohio, Florida Missouri, Iowa, New Mexico, Nevada are swing states where GWB won by less than 3 percent."
No, the GOP has a small natural advantage. Winning a state by a few percentage points, especially if you're, like Bush, an incumbent running in good times against an unattractive challenger, does not mean the state can reliably be placed in your (our) party's column.
However, incumbent senators, or at least incumbent Democratic senators, have a large natural advantage.