Why does 他回来了 sound fine but 他回来中国 sounds broken, and where does the place go?
The place goes in the middle: 回中国来, never 回来中国.
来 and 去 are direction tags that snap tight onto the verb, like 回来 or 进去. The moment you name a place, that tag gets shoved to the back and the place slides in between. So the verb and the tag split, and the place lives in the gap. English glues the place straight after the verb, which is exactly why 回来中国 feels right but lands wrong. This is the same 'split the verb' logic you already met with [separable verbs like 见面](/grammar/separable-verbs-62).
| Situation / Pattern | Formula | Natural | Avoid |
|---|---|---|---|
| Returning, no place named | 回 + 来/去 | 他回来了。 | 他回来中国了。 |
| Returning to a specific place | 回 + place + 来/去 | 他回中国来了。 | 他回来中国了。 |
| Going into a room | 进 + place + 来/去 | 他进屋里来了。 | 他进来屋里了。 |
| Climbing up a mountain | 上 + place + 来/去 | 我们上山去。 | 我们上去山。 |