This tendency probably improves the general level of journalistic objectivity in said magazines, but it also has a negative consequence. American opinion magazines, while contentious and prone to partisan hackery, allow their regular reader to empathize with, relate to, and root for a specific party. While I wish more people didn't agree with The National Review, more people using affirmative selections to determine their political preferences rather than choosing the lesser of two evils is unquestionably a boon to democracy.
In Mexico the default mindset, especially among the educated set would read La República Nueva if it existed, is one of cynicism toward political leaders. There is of course a great deal of political cynicism in the US, but magazines like those mentioned above help to balance and channel the cynicism; for most readers of TNR, you're pessimistic during the Bush years but optimistic during the Obama years. I don't mean to say that the cyclical partisan warfare in the US is a good thing, per se, but I do think it's better than the politically nihilistic viewpoint you see so much in Mexico: everybody is unredeemable.