This is actually a really tricky question that I always have trouble answering even for myself. However, it's important to remember that the thought is what counts when it comes to Omiyage. Now, even though importing ruined everything, the classic American bourbon whiskey like Maker's Mark or a good Wild Turkey is sure to be a hit in a country where drinking is a vital part of business communications. You can get Wild Turkey here, but it's very expensive, and I have yet to see Maker's Mark though I did a quick google search and saw it on a shelf. If your associates aren't drinkers, then local sweets are bound to be a hit so long as you have a neat story to go along with them (something like "the lady who makes these uses book pages from the Library of Congress to wrap her sweets"). Of course, this same "local is good" rule applies to alcohol, like wine. As a last tip, my general experience shows that what Americans consider "sweet" will make Japanese people freak out (in the bad way) over the amount of sugar is in the food. Be sure to buy sweets with painfully little sugar in them. Licorice is also a surefire way to encounter general disapproval.
Sorry about the semi-vague answer, but generally speaking a lot of Japanese people find it very difficult to buy Omiyage for business associates. Being from America, you have an advantage because as long as you buy something semi-local, you have a chance that whatever you get them will at least be new and interesting, even if they don't like the taste. If you need anymore specification I'd be glad to help!