Some questions about the British and American English.
You who do not have the accent of British English, tried to pronounce words like "newspaper", "water", "car", among others, and people of his region corrected you, being more familiar with the "R" American?

Continuing towards the "R" ... most of these words have such differences with the pronunciation of the letter, that is, try not to bend the tongue?

Question

Some questions about the British and American English.
You who do not have the accent of British English, tried to pronounce words like "newspaper", "water", "car", among others, and people of his region corrected you, being more familiar with the "R" American?

Continuing towards the "R" ... most of these words have such differences with the pronunciation of the letter, that is, try not to bend the tongue?

Answer

I had to read your question several times to understand what you are asking. Were you corrected, or is this just an idea in your mind?

A different pronunciation of R is not a problem, because the rest of the word is the same! You will find that many British dialects have a strong R, so something like the American R is not a problem at all.

By the way, there are several ways of pronouncing the R in the US - check on Youtube - so I'm not sure if you're simply mispronouncing R anyway.