The biggest difference between teams attending NCA and teams attending worlds: US teams all have the same age-grid year round (including worlds), they have (almost) the same rules (including worlds). Our age grids are different from those at worlds, our rules are (depending on which cheer association you belong to) different to those from worldsl, even the competition floor size is different. Except for very few people, cheer over here is not a business. It is run rec-style (coaches paid very little if anything, qualifying comps and the official nationals have comp fees that you guys would laugh about, etc.).
When one of your teams has a bad day/weekend at a bid comp it's not that big of a deal because there is another opportunity next week. We have exactly one bid comp over here. You have someone hurt the day before? Well, there goes your bid, because crossovers are not a thing in Germany. Getting your jitters out before worlds at a comp that is at least somewhat compareable? You're out of luck because the only comp you could do that at is the bid comp in May/June. Having athletes that safely progressed through all levels to be true level 5/6 athletes? Dream on, right now we don't even have all levels.
For those saying that athletes from teams that "don't do well" at worlds should not go there until they could hang with the big dogs: you do realize that those teams must have gotten their bid somewhere, right? And in order to get that bid they must have been the best at that specific competition, right? Every single team that is at worlds earned their right to be there. Just because it is not up to your personal standard does not mean that they shouldn't compete there.
And just because I'm in favor of keeping the three per country rule does not mean that I'm not heartbroken seeing OO5 not make finals, or that I am against expanding the rule (for example take top 10 scores + top 3 of each country).