4G is not, 3G should be possible on some. It could/should work on this one too, because the common 3G frequency bands in America are supported, though I have no experience of whether it will actually work then.
It probably won't work because the frequency bands of AT&T and co. are not the same as those supported by this product. This is also the case with many mobile phones, because the frequency bands in Europe and America are different. Maybe 3G will work, but I wouldn't put anything on it.