Some do verge into porn. (The aforementioned Black Bird definitely was. Poorly drawn porn to boot.) Most of them, however, were obviously intended to be either soap-opera-level fluff dramas, or, even worse, cutesy romantic pieces.
And there are some great series that eke out into the American market still for women. Lovely-Complex is probably the most honest look at teen dating, and its superficiality, I've ever seen. It's honestly a moving piece of work, if you're willing to invest 17 volumes' worth of time in it. And Red River sounds like the world's worst idea for a manga at first - a teenager from Japan is sucked through a pool of standing water and dragged into early Mesopotamian civilization - but turns it into a sprawling, beautiful, complex romantic war drama where the main character literally becomes the Queen of most of the Middle East, via her resourcefulness, kindness, and intelligence. The heroine is a fucking badass in Red River!
But what's baffling is that American audiences are eating up the more backwards manga - Black Bird is a massive hit stateside, as was Hot Gimmick, which is literally one of the most repulsive manga ever made. I won't go into the incredibly strange weirdness that makes things like Hayate the Combat Butler, which is a "boys" version of a plot of like nine hundred shojo manga (for those curious: boy is bought by precocious rich girl to be a servant to her, wacky hijinks ensue, and we would all be LIVID if this manga was reverse-sexed), popular. And I don't think it's a reflection of the ridiculously anti-feminist books that are also popular right now - Twilight really does go above and beyond in that department, but the only thing that seems to have stuck in terms of popularity about it is supernatural-themed media.