Yes, the phrase "Let's split the bill" is natural English and is commonly used in this situation. It typically means dividing the total amount equally among all participants, regardless of what each person ordered. In your example, where three people split a bill of JPY3,300 equally (JPY1,100 each), this phrase is perfectly appropriate.
Additional Notes:
If the bill is to be divided proportionally based on what each person ordered, people might say something like:
"Let's each pay for what we ordered."
"Let's settle up individually."
Conclusion:
The Japanese website's explanation is accurate in this case. "Let's split the bill" is natural and widely used when people want to divide the cost equally. It’s good to verify, though, since translation nuances can sometimes cause confusion. 😊