The reality is such that we overestimate the current military capabilities of the developed world as very strong, when its actually not that strong at all. It would take years or decades for the US and Europe for example to win and conquer Russia or China together, and it would take a substantial part of our economies, and it would ruin things at home, in a conventional war, if we could ever do that, even together. The US or Europe doing it alone is just unrealistic, because militaries arent really so strong as we think they are, and military budgets, efforts, equipment and such would need a massive upgrade and at least 25% of our GDP(and 25-50% national effort) to stand any chance at waging such a war. We would need at least 25-50 million man in armed forced to take Russia completely, and this is completely counting out nuclear weapons, and it would probably take a 100 million men to permanently conquer China in the same way, or even more. Thats when our current troop numbers of 1.5 million in the US and close to 2 million in Europe seems quite weak, and our equipment capabilities far below what it needs to really be as strong as some people want to think it is.
Remember that Germany during the second world war had a total over 20 million men in service.