your sentence would translate as: هذا المطبخ أمريكي
Notice the change in the definite article AL. Without it (as in the sentence above) makes "kitchen" مطبخ as predicative - so in English, this word must come AFTER "is".
When adding "AL" to it, then this word combined with "this" are all together a subject for the sentence, and must come BEFORE "is".
Actually this is just a trick you can think of mentally while translating. I didn't want to go deep into grammar.
Actually, the Ch in Bach is only a correct Arabic Kh in the English pronunciation of German Bach. In German we pronounce the ch as [x] while the Kh sound in Arabic is [χ]. Spanish J as in jalapeño imo is closer to Arabic Kh.
And the convention, as far as I know, is that Arabic Kh is 5 when avoiding confusion with که
Yes, some people do type it as (5) but the majority use (Kh). If the need rises to type كْهـ with Latin letters, well, sometimes we simply don't care if we know the other person will understand it, or simply some people (like me) would use a separator of some kind (I type it as "k'h").
Not sure about the outside, but at least here, there is a specific style of a kitchen which is called an "American kitchen" - it is a kitchen that is open to the living room without a door between the two, with a counter sort of thing that separates the kitchen and the living room.
On the other hand, away from styles, it could simply mean a kitchen made from parts from the US. As simple as that.