Revenue is not profit. It costs money to serve content. The EU has a 1.5x population of NA so that means it is only a third the revenue per user. The third segment has 6x population of NA so the revenue per user is only ~8% of a NA user and that population’s revenue stream is probably dominated by Japan, Korea, Australia and wealthy countries. At a certain point it costs more to serve content than ads will pay. Twitter doesn’t have the pockets to run a loss as an investment indefinitely so it needs to be picky about where it spends money.