It is such a sterotype that Chinese speakers mix up 'r's and 'l's that I always assumed it to be true. Is this the case and, if so, why? The tongue position is totally different.
As I understand, in at least some major dialects of Chinese (maybe all, I don't know), the /l/ and /r/ sounds exist but are prosodically restricted. The /l/ can only appear syllable-initially while the /r/ appears syllable-finally. This means that a Chinese speaker would have more trouble with an /l/ sound at the end of a word and also with an /r/ sound at the beginning of a word. This means that a speaker should be able to pronounce the /l/ in "ladder" but have difficulty with "red". This agrees with Jon Purdy's examples of yimier for "email" and luōqièsītè for "Rochester".
Korean has the opposite going on; that is, their /l/ and /r/ are in allophonic variation such that /r/ shows up syllable-initially and /l/ syllable-finally, meaning they would have more trouble saying the /l/-sound in "ladder" than in "feel".
In both cases, it would not be trivial for a native speaker of these languages to distinguish the differences between English /l/ and /r/.
It may seem strange that a language would have no difficulty pronouncing a sound in one position in the syllable but extreme difficulty pronouncing the sound elsewhere. However, in English, we have similarly restricted consonants. For example, the consonant /ŋ/ (the "ng" sound in "hanger" — yes it is only one sound, unlike "finger" which has the sequence [ŋɡ]) is only produced syllable-finally in English. But, in many other languages, words commonly begin with /ŋ/ (e.g. Swahili). So the difficulty you would have pronouncing "ngapi" (/ŋapi/) is the same type of difficulty Chinese and Korean speakers run into with /r/ and /l/ in certain places.
In Japanese, there is only one sound that appears in all positions within the syllable. Their /r/ sound is something between /l/ and /r/, and so every English /l/ sound comes out sounding like something "r"-ish.
I believe the reason is that, in Japanese at least, there is no Western L sound, therefore a native Japanese person won't learn to pronounce it (at least the Western way) at an early age.
In my Japanese language guide, the following pronunciation guide is given:
r - between l and r, example: gorufu
Take Off In Japanese, Oxford University Press
(gorufu is Japanese for golf).
So it would appear that the closest pronunciation to Western L is 'Japanese R', hence it sounds to Western ears that Rs are substituted for Ls.
The overall effect is called lallation.
Mandarin Chinese has both sounds, and there's typically no difficulty differentiating them. It's a Japanese stereotype (based on the fact that in Japanese these two sounds are allophones) that has grown to be applied to speakers of other East Asian languages. It might be compounded by the existence of facetious Chinese transliterations of English words, such as yimier for email instead of the literal diànzĭ yóujiàn, "electronic message".
Some dialects of Chinese have little to no erhua, the tendency to suffix words with an R sound, so they may have difficulty pronouncing an R sound syllable-finally, because their own speech never calls for it (compare Standard Mandarin nàr, "there", versus more Southern nàli). In addition, L is frequently used in transliterations in place of R syllable-initially, as in luōqièsītè for Rochester.
So it's not so much that these sounds are confused, but that they're just used in different contexts, and a Chinese speaker might conceivably have some difficulty with that. But again, this probably affects Chinese speakers less than Japanese speakers, who might find it difficult to differentiate between the sounds in the first place.
In east/central Africa (I'm assuming most Bantu languages), the R's and L's mix up as well. I, like the question asker, at first thought this was very confusing as R and L sounds for me as a native English speaker had nothing in common.
Unlike Asian languages, Bantu languages often use the same alphabet as English (minus perhaps a few odd letters like Q and X). In fact, the Bantu dialect I'm studying has native words with distinct R sounds and others with distinct L sounds. For other words, however, the R and L are completely interchangeable.
After many years of puzzling over this point and living in Africa, then Asia, then Africa again, I've come to this conclusion about the Bantu R/L swap: it is not so much a tongue position as a bit of a pinching in the back of the cheeks for both letters and a tendency to roll R sounds. If you roll an R, you will see how surprisingly close it comes to an L. When the L or R comes right before or after certain vowel or consonant sounds, it will almost always come out in the way we expect. Some English examples are paper, shirt, car, call, relevant, and hurry. Others, like my favorite "manicule and pedicule" place, the church where I "play", and the "riblaly" where I check out books are opposite examples. I think other West African languages may share this characteristic.
Chinese has many completely different dialects. It's so different in pronounce that I completely cannot understand most of all, such as Cantonese and Min Nan . But all those dialects share almost the some characters.
In my hometown, They cannot make a difference in 'n' (not 'r', our dialect hasn't this pronounce) and 'l'. But for me or most of the Post-80s, We learn Mandarin since the childhood. So we can make the difference.
Mandarin Chinese have "l" and "r" at the initial place of a syllable but not the end place.
The Chinese "r" is in fact different from English "r" or French or German; and in some dialect there is no "r", the mandarin "r" is pronounced as "n" or "y", e.g. Riben (=Japan) can be found pronounced as niben or yiben (compare Japanese "Nippon", Korean "Ibon", and English "Japan"). A lot of dialect have trouble with "l" and "n", in my own dialect I can differentiate "li" and "ni", but not "lan" and "nan".
Basically, Chinese can differentiate the initial "l" and "r" unlike Japanese (surprise and supplies are perfect example, I know such a joke about Japanese).
As the "r" and "l" in the end of a syllable do not show up in Chinese, many Chinese, including me, have trouble with this. I do not known how to pronounce "here" and "hill" properly. Hopelessly, I think other people like Google pronounced the same.