long lists of countries and cities in taxonomy

I used taxonomy batch module to create long lists of countries and city child terms which is essential to the organization of my site.

Now when a user goes to create content, he is presented with a list of countries, and their child terms (the cities). The user has to first find the city, then scroll down further in the same menu to pick the city. When every COUNTRY has a corresponding child CITY terms, the list is huge and unworkable.

What I want the menu to be is dynamic. After selecting lets say "USA", the menu would close and another menu would pop up with all the "USA"s child terms, ie New York, Los Angeles, etc. So this way the selection process is much easier AND the user by default picks both a country and city. The created content after being posted would be labeled by both COUNTRY and CITY.

So far I can't find any module that would enhance taxonomy to do this. I really hope its possible because the current system is unworkable for very long hierarchical lists such as a country-city.

Any suggestions?

Thanks