Absinthe is not ‘illegal’ in the US but the genuine stuff cannot be legally imported. It can be obtained from various vendors, via mail order, however.
There is a huge mythology built up around Absinthe. For the most part, it is just another alcoholic beverage, not a ‘drug.’ The interesting aspects are the ritualistic preparations, IMO. Analogous to cigar smoking, in some ways. Tastes like anis, BTW.