Translation:China is very far from the United States.
But "de" in Esperanto means possession, it is weird to use it when talking about distance. In Russian, we have a preposition to talk about distance, "от" (далеко от = far from), but in other cases from = из, (came from = прибыл из). For "of" (de/da) we just use genitive case without preposition (glass of water = стакан воды), but it is also never applied to distance
I'm not sure if I'm right, but according to an online Esperanto dictionary I've consulted, "for" means "away", but not necessarily "far away". I found this given example very helpful to understand what "for" implies: "Marta staris jam kelke da paŝoj for de ŝi".
"Fora", on the other hand, means "far away", but it seems to be an adjective that needs to be followed by a noun, so I'm not sure if it could replace "malproksima" here in this sentence.
Here's a screenshot: