Is there a reason that tax couldn't be imposed on the buyer, collected by Google at time of "sale" (click through by customer on ad), and remitted to the govern

Is there a reason that tax couldn't be imposed on the buyer, collected by Google at time of "sale" (click through by customer on ad), and remitted to the government, regardless of buyer origin? In other words, if I live in Montana (no sales tax) and I pay Google to display ads in Spain, I don't see a good reason to not have to pay Spain's "sales tax" (or whatever we're calling it) on those ads. I don't see why it should matter where the ad buyer lives, or where the ad clicker lives. I'm paying an entity in Spain, therefore the entity in Spain is taxed (and that higher cost ultimately flows back to me, the buyer). Or am I not really paying the Spanish entity when I buy those ads?