US Internet: Why has eCommerce accelerated and who is gaining?

To the surprise of many (including us), US eCommerce demand has been accelerating over the past four quarters. 2Q26 felt like a significant earnings cycle, not only because the momentum in US eCommerce continued, but also because 3Q26 guidance was constructive on GMV trends even against tougher compares. eCommerce stocks are now starting to 'comp the comp'. Over the past 2 years, US eCommerce growth was stuck in the MSD to HSD range; this year GMV trends have improved, with the industry growing ~10% and the largest platforms growing mid-teens, and penetration rates sit at 17% with several core categories at ~30%. We break down drivers of acceleration into top-of-funnel and onsite tailwinds. Top-of-funnel: the US consumer has held up well, tax refunds helped in Q2, the digital ad auction got more favorable (Amazon exited Google PLAs, Temu/Shein spending more rational), and AI-driven improvements in content recommendation and targeting from leading ad platforms are a symbiotic tailwind.