Most of us have only seen Williams play for USA basketball (U17, 3x3 and U19) and the results have been mixed. Of course, that's been true of other players who turned out okay (e.g., Maya).
Williams played in the U17 world championships in 2016 -- the tournament that garnered so much attention for ONO. Christyn was the 2nd leading scorer (11.9 ppg) while leading the team in shots attempted. She shot 37% overall (29-77) and 31% on 3-pointers (10-32). She did make 100% of her free-throws (15-15). With the exception of ONO, the entire USA team shot poorly so Christyn had lots of company.
Williams played in the 3x3 U18 world cup and won gold with teammates Decosta, Bailey and Littleton. I'm not aware of stats from the tournament but my memory is that Williams struggled from the perimeter.
Williams was on the U19 team that lost to Russia at the recent world championships and her minutes were limited. She often looked like the youngest player on the team. She made 31% (6-19) of her shots and 22% of her 3-pointers (2-9).