It's not the be-all and end-all, but when you struggle against countries with a population of 2.1 million - or 5 countries with a COMBINED population of 20 million less than England alone - there has to be something wrong.
My point is we're not scraping past the top countries, France or Germany, Portugal or Italy etc, we're scraping past relative minnows. And while I know it's not that black-and-white, just for the record Spain have 10 million less people to choose from than we do too. It's not a one-off, I've not even mentioned Iceland (pop. less than 400k), the signs were there then and in previous matches.
I would argue that the countries you mention have never really taken football that seriously as a top level, well established professional game like most of Europe do. USA more so, but only relatively recently.
My point is if you lose an FA cup match to McColl's Newsagents Paperboys XI, or just scrape a win, well that's the magic of the FA Cup innit, but when you do it time and again it's telling you that you have a problem. We all knew what would happen once we drew a major player.