I'll probably get alot of flak for this, but I think the story more resembles
something out of "Home alone". 

Here's a list of what bothed me..
R & A act like ten-year olds rather than teenagers. Running off with a
complete stranger?  I don't think so. Kids their age should know better than
that. Of course, you can justify that they no nothing about America, and
wouldnt know any better. But I think common sense would prevail.

I don't think criminals would hold up victims in thier car. (Just look at
Pulp FIction ;).) Try having them get out of the car into the alley. You can
formulate a bigger fight scene there, also.

By the time they reach the hospital, people should know that they are lost
and efforts to get them reunited with their family should be in effect. The
hospital is also the best place for another 'touching' Ranma & Akane scene. I
don't think they would leave the hospital so abruptly, either. You can try to
have Akane swindle a deal to have the hospital put them up in a hotel until
the family returns for them. Maybe a trick she learned from Nabiki.

How's that for C&C? Sorry if I got carried away, I'm used to doing it with my
other projects. All in all, I think it's a good story with lots of potential.
Work with it a little more and the future chapters you're looking for will
come that much easier.

-Paul