Maybe it is an issue in those countries where 'R' is hard to hear in spoken language or it doesn't exist at all, like in Japan. For me, coming from Finland, it is not so difficult. We have quite a strong 'R' by nature, but of course nothing compared to that Big R they are using in Scotland 

I agree 100% with your article, Uri. And of course, there is the other way around with us, Spanish native speakers regarding pronouncing the letter R in English. Ad what about the the R in German? O.o Siento que es como hacer gargaras, jajajajaja Greetings from Guatemala!

Eso es la mejor explicación que he encontrado. Gracias

There are a lot of good articles and videos out there about how to make these sounds. I never had a problem with 'r' personally but for me, as with a lot of English speakers the 'rr' sound was a nightmare. We just don't have that sound in our language and at the start I had no idea how to do it. But once you have that knowledge it isn't so bad.

If you can find some videos describing where your tongue should be and start off real slow you should eventually get it. I managed to do it I think after a week or so of consciously trying to do it, and I mean I could do it speaking really slowly and only where 'rr' followed certain vowels. But if you keep practising and increasing your speed it gets easier and I can now do it probably 90% of the time, its only when I'm speaking really quickly or there are lots of words with the sounds one after the other that I struggle. And I'm going to keep practising and trying to eradicate these small mistakes.