> Imagine trying to create a single set of laws to apply to all of the countries in North and South America at the same time.

I actually think it would be quite a bit easier than it is to create the EU. There's a lot more broad cultural homogeneity between the countries in the Americas than there is within Europe. Even on the topic of language you've got the vast majority of all peoples speaking some combination of Spanish, English, and Portuguese. And Latin America has a bit more limited geopolitical concerns than Europe does which makes managing some tensions easier than it might otherwise be.

But I'm not sure why you are considering "it's hard to create the EU" to be a defense against complaints or criticism related to the EU itself. Maybe it's hard and it won't work and the criticism is reflecting that and others are pointing out that it's a flawed task to begin with for some number of reasons. For my own part I think it has been a fascinating topic and a remarkable accomplishment of statesmanship to even get the EU to this stage, albeit like anything there are some very valid drawbacks.

> There's a lot more broad cultural homogeneity between the countries in the Americas than there is within Europe

No, not really. Unless you believe the Hollywood view that everything south of the US border has a Sepia filter

Intra-Canada commerce is a PITA in itself

Do you think Mexico looks in the eyes of half the central American countries? (Mexico being North America, yes I know)