If I buy food on a flight going from LAX to Tokyo on the airplane, will there be a domestic charge(US) or a foreign charge(Transaction fee)?

Depends on the airline.

Food is included in your ticket price on international flights

Depends on the airline. If it's a US airline and a US card, then it'll be a domestic charge. Otherwise, it's an international transaction.

Food is usually provided on international flights.

Most airlines will have USD transactions.

depends on the airline. I fly Delta and even on flights where a US locn is not the start or destination, all my onboard charges are non international charge.

No because you are in the air so are not bound by country tariffs. Buying food on a plane is different to say, buying perfume, because you will not be importing the food at your destination (because you've eaten it).