Although Robusto has already written an excellent translation, I thought this may be a work that would benefit from multiple annotated translations, so here is another. :-)
Short translation: the author doesn't like (or claims not to like) the Super Bowl, but watched it anyway. [Aside: for comments in a different vein from someone who likes it even less, look here.]
The effects of 45 (or XLV, if you must) direct slams to the head could be clearly seen Sunday night on that annual American CAT scan called the Super Bowl.
The Super Bowl is the final game of an American football tournament, and watching it is an annual American ritual. There have been 45 Super Bowls so far, the latest being denoted Super Bowl XLV. The author parenthetically finds the use of Roman numerals somewhat unnecessary or pretentious. Then, he effectively says that each of the 45 has been a "direct slam to the head". This is both an implication that it is a head injury (affecting the collective intelligence of America) and a possible allusion to "direct slams to the head" that may occur during the course of the violent game. Anyway, the effect of these brain injuries, he says, could be seen on Sunday night when the Super Bowl was held, because (the author thinks for some reason) that the Super Bowl is a CAT scan (a scan that, among other things, is used to determine the extent of internal injuries) of America.
There is a bit of a mixed metaphor here: is the Super Bowl itself both a slam to the head and a CAT scan? Perhaps the 45 injuries are the 45 championships (tournaments), with a part of them—the final, the Super Bowl—a CAT scan?
Whole parts of our collective cerebellum now show up as having the color and consistency of old gum.
When chewing gum gets chewed too long, it loses its color, and its consistency turns into a uniform pulp. He believes that much of the American brain ("collective cerebellum") has now been turned into the same consistency. (This seems to be a comment on the state of the American brain in general.)
Too many insipid Black Eyed Peas songs will do that to a civilization.
Black Eyed Peas is a band which performed during the Super Bowl. The link is to a fellow author who found the Black Eyed Peas performance underwhelming. Our author takes it further, saying that they have had "too many" songs, and that they have been bad for the civilization as a whole.
There is another confusion of metaphors here: is the cause of the battered American brain those 45 slams as earlier stated, or too many songs by Black Eyed Peas? Apparently the author thinks it's both.
The cheese really is baked into the crust.
The cheese (cerebellum) has become baked into the crust (skull). A further description of the brain injury. (Robusto has the further insight that it's a line from a pizza ad.)
Of course, cheese baked into the crust doesn't really have the color and consistency of old gum.
But willingly, like achy old pros, we returned to the holy rituals of this brutal game, this billion-dollar boondoggle, tweeting our delight that seven-layer dip has somehow become nine.
Despite all the "ache" (of the head injury, probably) caused by the Super Bowl, we (meaning "I") willingly returned to the game. The game is a holy ritual, is brutal, involves billions of dollars in costs and revenue, and is a "boondoggle" (a project that's a waste of time and money). Seven-layer dip is a dish that is typically consumed as part of the Super Bowl ritual. People tweet about it during the Super Bowl, and some are delighed that the scope of the dish has been expanded to include nine layers. Apparently the author thinks this is too frivolous a topic to be posting on Twitter about (in which case he misunderstands Twitter).
Distraction is the real attraction, which gets a little more true each year.
The Super Bowl spectacle includes not just the game, but also musical performances and special made-for-the-occasion commercials. Some people claim to be watching the event for these "distractions", hence they are the true attraction. (Aside: One must marvel at the marketing genius that manages to turn ads into attractions, but that's another story.) He also thinks it "gets a little more true each year", perhaps because the sideshows are getting grander in scale and on their way to eclipsing the actual game.
And that's just the first paragraph. An enormous amount of cultural context can be encoded in a few sentences. :-)