There are, of course, programming languages that have non-English keywords, they're just not very popular.
I guess if you're learning all of C/C++/Java/Python/etc... the "English" keyword meanings are a tiny/trivial part of what you need to learn anyway.
Also, using English means you only need ASCII, and a US keyboard layout which allows easy entry of the printable ASCII characters. For Japanese, Arabic, etc... you need need Unicode, input methods, UTF-8 / UTF-16 etc., all of a sudden there's a whole lot more to go wrong than if you use English in ASCII.
I guess if you're learning all of C/C++/Java/Python/etc... the "English" keyword meanings are a tiny/trivial part of what you need to learn anyway.
Also, using English means you only need ASCII, and a US keyboard layout which allows easy entry of the printable ASCII characters. For Japanese, Arabic, etc... you need need Unicode, input methods, UTF-8 / UTF-16 etc., all of a sudden there's a whole lot more to go wrong than if you use English in ASCII.