ZippityDooDah said:
At the start...
Chinese suppliers mostly relied on genuine (though I won't call them legitimate) 3PL operations as their US "warehouses," and these facilities were nearly always Chinese-owned, Chinese-run, and Chinese-staffed.
Later on, certain suppliers shifted toward recruiting private people—often originally buyers or local sellers—to act as "warehouses." Under the 3PL arrangement a supplier might keep 1 to 3 warehouses, but with this newer approach they brought in multiple individuals and scattered stock among them, capping what any one "warehouse" held at a level they could afford to write off if that person cheated them. That is chiefly why a lot of suppliers struggle to track inventory, run into delays, or fall back on shipping from China: these folks running a warehouse out of a garage or spare bedroom are, at best, tracking things with email and spreadsheets rather than a WMS (warehouse management system).