> What I am saying is that in English, after learning 26 letters, you can read any combination of them. If you try to see how many possible syllables there are, there would be many thousands. Combinations like "eng" "lish" can't be properly put in Japanese phonetic characters because you can't put "eng" directly, you have to use "en gu ri shu", inserting vowels all over the place. Japanese can't properly learn English because their brains are trained with much fewer possible syllable sounds and they can't make the jump.
This claim is significantly misleading.
Every language has its own phonotactics, which includes allowed and forbidden sequences of sounds.
https://en.wikipedia.org/wiki/Phonotactics
English and Japanese both have their own phonotactic structures. While English's phonotactic rules are much more permissive than those of Japanese, and allow more different sounds to be used and to be combined in more ways, and while these differences do affect what native speakers of each language can easily say (or recognize other people saying!), it's a mistake to say that English allows everything while only Japanese has restrictions.
Both languages have restrictions, and both have restrictions that some other languages don't have. For example, Slavic languages allow consonant clusters that English doesn't. Hindi allows distinctions of aspiration in arbitrary locations where English requires particular aspirations in particular positions or at least considers this distinction non-phonemic (and hence extremely hard for English speakers to learn to appreciate even when both sounds in question are part of their phonetic inventory).
If, from noticing the more extensive restrictions on sound structure in Japanese, you get the impression that English speakers can pronounce any sequence of letters from our alphabet, you're missing something significant about how English works.
Edit: as other people have noted in this thread, these differences between these languages are also probably not originally due to differences in writing systems. Often languages that share the same writing system have different phonotactic rules (and different sound inventory, for that matter). It's more likely that many of the important differences predate the writing system, although it's true that the writing system can influence how people learn and think about their language and how it changes over time.