"I often wonder what noises people that do not know English make if they are pretending to speak English."
In Ghana (where I grew up), whenever someone wanted to imitate someone with an American accent, or just more generally, an impressively fluent speaker of English, they would say something like:
"Risss prss strssp tris sprriss" etc.
This is because most of the languages spoken in Ghana end their words with vowels. Indeed, a lot of what happens when you adapt words from English into the local languages involves the dissolving off the consonant at the end of the word, or grafting on a new vowel to it. For example, in the Ghanaian language Twi, car becomes "kaa", or "bucket" becomes "bokiti".
For people in Ghana to whom English is a second language, or for those that simply picked up the Ghanaian-English accent and know nothing else, clipping the open sound of a vowel and stoppering off the word with a consonant is either unusual-feeling, or just plain impossible. Although it's not a one-way street; there are diphthongs in Ghanaian languages that native English speakers can never seem to get right...
In general, I'd take a guess that for each language, speakers pick up on the features that make English different from their native tongue, and exaggerate them when trying to fake English.