I think "We only show americans" is part of it but not the only reason. TV Networks like to be sure that the same names will always be in the latter round of tourneys. Familarity is a good thing when you want casual fans to watch. Generally the woman always make the latter rounds so they feel comfortable showing non-american women who always win (Graf, Sanchez, Hingis for example) Last year was the most unpredictable year for women's tennis in the open ara. 4 different winners, 3 first time winners. There hasn't been enough time to see which of the 3 are the read deal. But let's be honest Sharapova is popular more for her looks than her results or american ties. I remember them showing her in '03 Wimbledon when she was very low ranked & playing on an outer court. I also remember Harkleroad shown a few times at slams, regardless of her low ranking. Doubt that will be the case if, say Monfils was playing. If Mauresmo, Clijsters & others looked like Kournikova, there would be even less men's tennis being shown.
I think Federer is getting more respect from american tv than safin or hewitt ever did. that's because he wins so much, it's hard to ignore him. out of the non-americans, he will definitely get the most airtime at the french & wimbledon. certainly far more than dent or fish. those 2 are american but are unlikely to ever become familiar with american fans because of their results. dent was shown last week because he played safin, the aussie champ. If he was playing nalnadian, chances are it wouldn't be on center court. fish & dent are not elite players & networks care more about familiar faces than nationality. yes agassi & roddick get priority,but they are top players who generally make the later rounds of big events consistently.
The 90s were the best time for american men's tennis(in terms of titles) but i never felt it was bigger than the womens game which just had graf, seles, & sanchez. I would say it was a tie, both sports were treated equally(as they were in the 80s as well)
But in the late 90s, they was a definite shift to the women. For the most part that is still the case today.
It's also hard to judge these 2 events, because the sisters/capriati/henin didn't play last week, so men got more attention. This week davenport/capriati aren't playing. If they were, the women would be even more of a focus.