One bit of truth is just that if you’re an English speaker, the career benefits of learning another language are rather small outside of specific reasons. And as far as being in the US goes, depending on where you are you may even run into more Cantonese speakers than Mandarin.
Chinese and Japanese are fundamentally different, but a few things. Cognates, while not as obvious as you’d think many times, there’s enough there to have some idea what’s going on. But on the other hand, you do have to worry about both False Friends and False Cognates. Not really needing to learn Kanji a second time. Most simplifications are pretty obvious and the ones that aren’t aren’t that numerous. Although there are Kanji that are used only in one language or the other, it’s still much more reduced.
On a different level, other areal features can help. Understanding the Topic-Comment structure, as well as the use of particles are two things that come to the top of my head. But many times I simply find it easier to see the explanation of a grammar point in Japanese than in English. Also in some cases, a grammar point pairs more directly with Japanese than with English.
The fact that using Japanese rather than English can be explained about the fact that I learned Japanese as an adult using that technical background while I didn’t do that in English. So the Japanese can sometimes just make more sense. On the other hand, second (non-native) language interference is a real issue in a third language.




