We live overseas, and the students from our country who get accepted to Ivy League schools tend to be number one (or top 5 in the country) in their age-group for a particular extra-curricular activity. They don’t necessarily have to have done a lot of ECs, but they definitely have stood out as the absolute best in their age-group for their activity (can be sports, music, or international award in academic pursuit).
They also have been strong students academically, but haven’t been as stressed about academics as American students b/c Ivy League often wasn’t on their radar until their last year of high school (i.e. haven’t worried about rigor of class schedule, SATs, etc).
SLACs are great schools to consider because there may be fewer international applicants simply b/c they don’t have the same name-recognition overseas. I highly recommend looking into a variety SLACs to see if they might be a good fit for your D22.