hah, You should buy one of these,
<img src="http://images.jlist.com/c3/gf1whno2.gif">
Although I think that Americans that understand Japanese are few, they do seem to like kanji and katakana shirts. Most Japanese have some experience of English since high school. It is a shame that Japanese books don't sell as well as porn memberships. It's definitely and untapped market... "common kanji tattoos" would do well especially amongst the otaku.