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Yes.

Under System Preferences, go to International. Then drag English to the top. Restart your MacBook and you should be in English.

If you want to use both at the same time, you can create an "English" ID/Account. Set it to English as shown above. Then you can switch between Japanese and English by switching between accounts.
 
The big issue is the keyboard layout.

My PB15 has a Japanese keyboard. At first it was hard to get used to it. But now I rather like it.

I believe that you can request a US keyboard instead of a Japanese one on most products. It might cost extra. Definitely worth asking about if you prefer a US keyboard.

All Apple apps work fine in US or Japanese. If you purchase a Japanese version the documentation will be in Japanese but other than that it works fine with English. In the Ginza Apple Store, I know that they sometimes will have English versions of some applications. That way you can have the documentation in English if you want.
 
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