I want to say "Yes, we can", but at the same time i dont think we really can. They over use facial expression when they arnt really needed, the art styles tend to be far from what most would consider "anime" art style itself, and the stories tend to be very Western, where as anime tends to stick to Eastern areas or Space.
I wouldnt consider Teen Titans, Avatar, The Power Puff Girls, Ben 10, Star Wars: The Clone Wars, or "Korra" as anime. They are extremely western in both art, and story. Its american animation with anime tendencies in it. You can use shading like an anime, and facial expressions like one, but that doesnt make it one. Then you have things like Megas XLR which is american animation, but very Eastern in story, comedy and inspiration. Its not "Anime", but its close to it, much like Samurai Jack was. They didnt over use comical facial expressions, they didnt try and hamfist jokes to use the facial expressions, they were just themselves, and that made them great.
I would say The Boondocks is closer to anime in art and spirit, but not in ideal. Everything in the show, from its writing, characters, plots and comedy are weastern. Its nearly there, but it stops just shy of what i would consider "Anime" and not "Western Animation". Its right on the border.
But Afro Samurai is what i would consider "Anime", if right on the border. The Art style is spot on, the characters and their backgrounds fit extremely well to the genre, the humor is very well placed, and never hamfisted in an unnecessary way, and above all, the story itself is extremely eastern in style. A style which is full of grim moments, heroic losses, comedic backdrops and deep presentation. Nothing "Good" ever happens, which is also something i hold to a far more Eastern style of Animation. In american animation, the hero will ALWAYS win, he will ALWAYS live, and he will ALWAYS be the hero. His choices will never effect anyone in a real negative way. He never has to condemn the innocent to a fate equal or worse the death. He barely has to condemn the Evil to such a fate. In Afro Samurai, he regularly has the choice of just "Stop killing". He could easily just throw away his headband, and spend the rest of his life drinking lemon-aid. He is no more a hero then a villain, arguable he IS a villain in the series with how much pain and suffering hes caused for a headband.
Can americans make anime? Yes. But we dont. We barely even put effort into it, or trying to do it. And when we try, its close, but distinctly western in story, style and character. We have done it, and we might do it again in the future, but its going to be rare.