^^ It's probably why they can't win in Europe!
Seriously though, for all Uefa's protestations, most European teams are in the same boat, and it's not necessarily made much difference to the national games of the respective nations. Italy won the WC, Spain won the EC and England, well, are still crap, but then, we almost always have been. Trying to attach reasoning to that insinuating that it's because of the 'influx' of foreign players, and the lack of 'homegrown' talent is erroneous.
Patrick Vieira, great player at Arsenal. Can't say as I've seen much of him while he's been playing in Italy though, but when I have he's not looked the same player, but then, he wouldn't, he's older, and in a different team.