What I mean to say is that for teams to get better, they always have to want to get better and they have to work and practice for it.It is taken for granted that teams will want to get better (and accordingly train and commit) and therefore is a common denominator to both options (Yanks coming and Yanks not coming) and can therefore be factored out, which leaves us with....teams will get better if we have better teams to play against.
I cannot for the life of me understand your reasoning here other than flagging up something that should be obvious to all.
As you can see, there are already some teams that compete in CPL which are somewhat outclassed (Or out"guested") by the top teams in the League, kind of like with Ultimate in the NXL, and you don't see them improving immensely from event to event just because they play against better teams.
Ultimate plays against the world's best teams on a regular basis and yet in 3 years in the NXL they have only won 1 (That's right, one) match.
The European teams that have managed to elevate themselves to the "American" level, such as Joy Division and the Russians, did so because they adopted a very serious training program, and because not only did they have the dedication from their players, but also the conditions to be able to practice that much.
If you are an underfunded European team whose players need to have a fulltime job in order to support Paintball and who are not likely to have the availability to practice 4 or 5 times a week (Unlike teams like Joy Division or the Russians) then you will find it pretty much impossible to adopt such a training program.
So basicly, you are running this discussion on the basis that all European teams would have the possibility, the funding to allow them to practice and the possibility/will to do it when in fact I don't think alot of the teams do.
So long story short, I don't think that European is in a position right now where it would be able to fully benefit from the presence of American teams, it would just contribute to benefit a few select Euro teams and drag the others down.
So in my opinion, there are still alot of other things that need to be sorted before having American teams over can be a point of discussion.