Chances that native speakers can't understand each other

I live in Hong Kong. I have started learning English since I was six. But I
learned it the hard way as I learned with my eyes rather than my ears. The
English taught over here is claimed to be British, but actually it is a
mixture of British, American and Chinglish, while Chinglish is the main
ingredient.

It is very difficult to talk to a native speaker over here, so I bought a
lot of Hollywood movies to learn. I dare not say that my accent is American,
but my "ears" are American for certain.

I can understand Hollywood movies without any difficulty. But recently I
bought some British sitcoms, it surprised me greatly as I could hardly
understand.

I want to know if it is possible for a native speaker to have similar
situation. Or should I put it this way? Will a native English speaker have a
chance of talking to another native speaker without understanding each other for more than 50%?

The sitcom is The Office. I turned on the Eng subtitles, so I noticed that
some of their pronunciations are different from my Oxford dictionary.
Please help.

It really depends on what the person's accent is for me, but I usually don't have a problem understanding the Australian Accents, or the British Accent or the NZ accent, I live in the USA, the one accent I have problems understanding is the Brooklyn Accent, but once i heard it more, I understood them more, so just rent or buy more movies that have a british accent to them, you'll learn how to understand them eventually, trust me, it does work.

I'm sure there are many Americans who would have trouble with several British accents, such as Glaswegian, Geordie or Black Country, especially as most Americans are rarely exposed to these accents. Cockney might be difficult but almost everyone has seen My Fair Lady. Most Brits do pretty well with American accents because of all the movies we make.

The American accent I have trouble with the most is the Jerry Springer "Hillbilly Accent." They must just take a helicopter and pluck those people off of Appalachian mountaintops.

Ryan