The other European countires could have shut down Germany's sea power
quite easily, kept *any* U-boats from going out to harass convoys, and
gotten a lot more support in during the 1940-1942 years. If they had hd
carriers available, they could have had strong fighter support across
all of Europe during the entire war, and D-Day could have happened a
couple of years earlier.

I don't think that they had a crystal ball to see the future. There was no
reason to expect the fast fall of France and BEF.
So your suggestion is that Belgium and Netherlands should have mustered a
strong navy with consirable carrier force? Do you have any sense of reality?

And Sweden, Finland the Baltic countries etc. had to consider the threat of
Soviet Union which was atleast as serious as the threat from Germany. Most
of the countries in Europe would have been better of with less navy and more
emphasis on army and airforce.