Like "Smashing Pumpkins", who are neither pumpkins nor do they smash things, "root beer" has one of those misleading names, particularly to those who are uninitiated in its carbonated delights. The Japanese, almost universally, are unaware (some might say blissfully so) of what root beer is.
This fact was brought home rather strongly at my former office when one of the salesmen was foraging in the company refrigerator for a leftover summer gift beer to imbibe "after work". For those who don't know (or remember that I said it before), it's common for companies to receive cases of beer as summer gifts from other companies they do business with. The salesman tunneled his way past the dozen or so bottles of green tea, oolong tea, Coke, and whatnot with about 1/8 of their original contents placidly clinging to the bottom and merrily growing bacterial cultures (because they are certainly never finished off nor tossed out by their owners). After several minutes of brow-furrowing concentration and digging around aged, near empty containers everyone was too polite to throw out, he emerged triumphantly with a can of my husband's A&W root beer. The salesman saw the word "beer" and assumed that he'd found his prize. You can imagine how let down he was when we informed him that root beer was not beer but a soft drink. The "root" part always confuses them, as well, and explaining about sassafras doesn't tend to help matters in this regard as I think they can't conceptualize how something goes from being a root to being a carbonated beverage.
After a rather imprudently large order from the Foreign Buyer's Club, I had to leave two cases of root beer sitting near the entrance of the apartment on the kitchen floor for a few weeks. Almost every one of my students said upon seeing these cases, "is that beer?" I explained to them that it was a soda one could only get from the U.S. In fact, I gave two of them each a can to sample because I'd done a food lesson with each of them where we had talked about items you could not get in Japan. It was also rather timely as the day one of these two lucky students got a can, we'd been discussing different vocabulary for "good" and "bad" and I told her that she'd probably find the word "revolting" especially useful after sampling the root beer.
Both of my students hated the root beer and said that it tasted to them like unpleasant medicine. However, one of them had split her can with her brother and she said he really liked it and had consumed the remainder by himself. I believe my husband also has given root beer to his students (as well as another much disliked "treat", black licorice) and found that there are always a few who find such things tasty but most think they're disgusting. I tend to like this sort of sharing with students both because I think it's good for them to have first hand experience with the foods that are discussed with them and because they're so fond of asking foreigners about the more vile Japanese foods they know we're going to hate (natto, primarily). It's a little bit of table turning to give them something we know they'll hate.