To address the OP directly, a sci-fi novella I once read described English (as heard by a foreigner) as a language that sounds like barking dogs. As a native English speaker I’ll never really know if that’s true, but as a student of other languages, I find it highly plausible.
Breaking a language up into the constituent sounds that we describe as vowels and consonants is a useful way to describe a language, any language.* This is not to say that this is the only way to describe a particular language or that it is the best system for all purposes. It is a useful way of describing which sounds distinguish meaning in a particular language.
Any system of cutting up a language has a certain arbitrariness to it and won’t reflect the smear of sound that is spoken language (which is what the system we are talking about is designed to work with), nor is it likely to reflect all of the nuances of what our brains are doing when they are processing these sounds. Phonemic description nevertheless does a pretty good job of describing the pertinent information about a sound system.
It’s worth pointing out that syllables are the basic building block of all languages that we have ever encountered. Every (spoken) word will be in the form of one or more syllables. A syllable can be further broken down, if you wish to do so, into a consonant and a vowel, but that doesn’t negate the existence (or importance) of syllables.
No one is saying that Japanese speakers don’t think in terms of syllables. Nor is anyone saying that it’s not useful to describe Japanese in that way (indeed it is very useful, and you would probably miss some important insights if you ignored it). What is being said is that you can meaningfully describe Japanese in terms of consonants and vowels and that it will provide useful insights about the language.
*Perhaps some day we will discover a language for which this isn’t the case, but it’s not really very likely–Japanese is definitely not this language.
If they do “think in terms of syllables,” whatever that is supposed to mean, there’s no reason why they would do so more than any other language speaker, nor is it because of the way they learn to write, years after they start speaking.
I’ll say it again: Would this line of reasoning mean that all European language speakers are “thinking in term of consonants and vowels” when they speak?
Well, as a Frenchman, I can say that there’s definitely a line between American English (which sounds understandable, smooth-flowing - this due to the countless entertainment I’ve been subjected to) and British English, which sounds… schooly and sometimes cryptic and exotic somehow.
When Ingmar Bergman was asked this exact question by Dick Cavett some [del]years[/del] decades ago he replied, somewhat apologetically, that it sounded like dogs barking.
Fascinating thread!
Although, as an English speaker from South-East England, with only the rudiments of linguistic knowledge, I have been thoroughly confused by it…
I had never realised that anyone could pronounce ‘merry’, ‘marry’, and ‘Mary’ in the same way (even the sound files provided seemed to make them sound far more similar than I had ever heard them) and yet I pronounce the ‘e’ in ‘pen’ the same as I do in ‘let’, and ‘father’ sounds the same as ‘lather’ when I say it. Out of interest, how do you pronounce either of those pairs differently from one another?
And to return to the original OP, I’ve always been told that English sounds very harsh, and quite Germanic. I’d be interested to know if anyone has any specific opinions on how my accent sounds (American opinions welcome :D).
In some dialects, ‘pen’ sounds like ‘pin’, and the vowel in ‘lather’ sounds like… well, I was going to say ‘latter’, but I’m not sure you’d say those differently. Perhaps in your case ‘leather’ is a good approximation for how I say ‘lather’.
Well, it’s a Germanic language, so it would be surprising if it didn’t sound thus!
I don’t detect an accent in your post. 
It’s funny, when someone asks me to say the writing utensil I say “pen”. But when I’m just asking for a pen I pronounce it “pin”.
Lather, here, is pronounced like rather. Wait, that won’t work.
My History of English professor said it’s like this. “You walk down a path to go to a dance.” Path is the one we’re using. Dance is the one you’re using.
Wait, I might have that reversed. Too late for edit window.
Yeah, he doesn’t even use any Britishisms 
Most second-language speakers can’t distinguish/identify accents in their second languages; we can tell that John-from-Austin and Jerry-from-New Jersey speak differently, but in general we won’t hear John and think “he must be from Texas”. If we’ve met, say, a group of two dozen people from South Carolina and been able to compare their collective speech with those of a few dozen people from other parts we’ll be able to identify that “this person’s accent/dialect is similar to that of my coworkers from S.C.”, but in general all we can tell is “these two people have different accents/dialects”. Given how many times I’ve encountered people who claim to speak Spanish as a second language and who think that all Spaniards have the same accent, the rule appears to hold for any second languages.
I’ve watched coworkers dissect accent variations village by village in Catalan, or within a single Andalusian province for Spanish; I can do it for villages near mine for the Aragonese family of Spanish dialects. English? Without visual clues telling me “this guy is from India” or mentions such as someone’s nickname being “Brooklyn”, I can tell you they sound different and try to dissect in which ways, but I won’t be able to pin each one’s accent on a map - and it’s not as if India has a single accent, no more than the UK or US do.
Not by me, although I do pronounce “marry” and “Mary” the same. “Merry”, to the the extent I pronounce it at all, has a shorter vowel.
It’s my understanding that in the typical Southern American accent (really Southeastern American), in which “pen” and “pin” have merged phonetically, some people will say “ink pen” if it’s a pen to which they’re referring.
No, we usually just take it in context. If we want a pen, it’s usually obvious. If we want a pin, it’s a “push pin” or “tack”. Or it could also be obvious in the context of the question.
At least that’s how it is 'round these here parts. 
In some English accents I’ve heard (mostly from my TV watching, mind you), the words “cat” and “can’t” are pronounced with approximately the same vowels as we Americans use in “lather” and “father”, respectively.
John Cleese, for example, speaks in the way I have in mind. (He and I would agree on how to say “cat”, but not “can’t”.)
When I was a wee lad, me, my brother and some kids from the neighbourhood would re-enact scenes from our favourite movie - Ivanhoe. The thing is, though, that we would replace all lines (yes, every single line) with the words “scrachum brachum.” Because, you know, English.
Like so:
Smokin’ Hot Olivia Hussey [wistfully]: “Scrachum… Brachum…”
Sam Neill [harshly]: “Scrachum brachum! Scrachum brachum, scrachum brachum!”
Smokin’ Hot Olivia Hussey [afraid]: “Scrachum! Brachum!”
Sam Neill [suddenly mysteriously tender]: “Scrachum brachum! Scrachum… Brachum. Scrachum brachum. Scrachum brachum. Scrachum… Brachum.”
It’s high time somebody pointed out that English-speaking zombies, if they can speak at all, rarely manage more than a few grunts and monosyllables, much like Tarzan or Frankenstein’s monster. That’s what they sound like.
It’s the least I can do after repeating my own post from two years ago.
Atlantic Canadian chiming in here.
When I was learning Spanish I understood what was being said to me by native speakers a lot faster than I learned to speak it back. I could distinguish where a word starts and ends easily, etc. But after eleven years of public school French, all I hear when anyone tries to speak it at me is one long sound. I swear I can’t even pick out “bonjour” in there.
Last week I asked a Polish friend of mine what English sounds like and her answer was: “Like guys with noodles in their mouths.” Hehe.
I asked her what people say Polish sounds like, 'cause I’ve never heard Polish, and she said to English speakers it sounds like a broken radio.
Yes, but this isn’t always because they can’t hear the differences. Once someone mentioned to me that the sing-song Spanish accent is Mexican, I could immediately identify a native Mexican accent easily, versus Costa Rican, Peruvian, Castilian, etc.. My Spanish is terrible, but I am actually very good at imitating pronunciation. When I’m in Costa Rica, as long as I keep my sentences short and simple, the locals often mistake me for a fellow Costa Rican, even though I’m a redneck from rural North Carolina, with the accent to match.
I have noticed that my ability with this sort of thing appears to possibly be genetic. My daughter’s mother can’t do foreign accents or impressions of other people’s speech at all, but I’m pretty good at it, and my daughter is phenomenal at it.
This doesn’t seem to correlate with musical ability, oddly, though…my daughter’s mother is a very gifted singer, and I’m a professional percussionist, but only I can do accents and impressions.
I used to think that people from other countries were just lazy/rude in keeping their thick foreign accents, but now I’ve realized that people vary tremendously in their ability to change their accent.
And I already said that, d’uh. Last sentence in that quote.