Fatuous One said:
Also, who says that Keitaro can't have picked up a girl in America? Granted, that might deter from the story, but it'd be interesting for Keitaro to try to make a long distance relationship work... while also getting closer to the Hinata girls.
On one hand you have his girlfriend waiting for him in the states, on the other hand you have girls "curios" about him at two steps. And to top all that the promised girl, which he may or may not remember.