The Android smartphone market in the US is quite different from Europe or Asia, in that there are fewer options, especially at the mid-range and low-end. But even when we're talking high-end, one thing is obvious - all of the top shelf devices in that market use a Qualcomm chipset. No MediaTek anywhere (and no Exynos either, for what it's worth). And that's despite the fact that MediaTek's 9000 series chips have, for a few years now, been very close in performance to Qualcomm's latest and greatest. The situation will thankfully change later this year, when, for the first time, a "premium"...
Source: https://www.gsmarena.com/highend_mediatekpowered_smartphone_to_land_in_the_us_for_the_first_time_this_year-news-62702.php