A lot of the arguments Jehovah's Witnesses make in favour of their religion can only work because they are a very small religion and are spread so thin. Nowhere in the world do JWs make up any kind of majority or even significant minority in any country or city. Considering how JWs would have to work with larger populations exposes these arguments, for example:
'We are the only group that preaches the good news!'
Imagine if a country's population embraced the JW message in such a way that as much as a third, or even just a quarter became JWs. How would the preaching work in that country? It wouldn't! If every JW went out preaching the territory would be covered in well under an hour every Saturday morning! Add in pioneers and the requirement for MSs and Elders to get 10ish hours a month, and the preaching work would be ridiculous, houses would be called on every few hours or less. There would be outrage among non-JWs and the Society would have to bring in new rules allowing only a few select members to preach door to door, and take away the reporting requirement for counting it's members in this country.
'We don't get involved in politics!'
Again, JWs don't generally have to! But what if over 90% of a country was JW, or the whole 100%, they would have no choice! They would have to have politicians decide how much you will be taxed, what that is spent on. Would this mean they were putting faith in men rather than in God?
JWs also like to criticise other religions who restrict their religious freedoms with their political power. How would the JW country deal with freedom of speech and worship? What would be the response to apostates printing their articles in newspapers? Could Ray Franz's books (or Harry Potter!) exist in a JW state library? Would evangelical and Catholic missionaries be allowed to preach in their country without fear of harrassment? What would happen to df'ed members? It is horrible just to think about it!
And where would they get all their University trained professionals (i.e. Doctors) guess they would have to make exceptions!
'We don't get involved in war!'
Well, even in a full JW country you don't have to have a military. Not all countries do, and JWs would deny they would ever do this. But they would certainly have to get involved in foreign politics, and if a neighbouring country declared war would they really not petition the UN or some other evil group to protect them, with force if necessary? I can't believe they wouldn't, and how could they then look down on soldiers when they had them fighting to protect them?