Posted July 10th, 2013, 12:01 PM
Whether you go through Passport Control at any European airport depends upon where you're coming from, and where you're going.
If you're arriving from a Schengen country (a list which is similar to, but not exactly the same as, the EU), and departing to a Non-Schengen country, you will have to leave the Schengen area of the airport to do so, and you'll pass through their Passport Control in the process. Once you leave the Schengen area, you're considered "in-transit" and you've officially exited the Schengen group of countries.
We have connected through CDG on our way to and from Egypt. In these instances, we never had to leave the in-transit area, and never had to change terminals, no passport control, etc. Though we were in France, we never technically entered the country. We were "in-transit" which made it really easy!
On the other hand, when flying Rome-CDG-JFK, we did have to go through Passport Control in Paris, and change terminals from the terminal handling intra-Schengen flights to the international terminal. Flying from Budapest to the US would be analogous to this arrangement, as Hungary is a Schengen country. This would be similar in any of the other airports mentioned - Frankfurt, Amsterdam, Munich...
It comes down to which airport is most efficient at making that change... Agree that CDG is big, and connecting is likely to involve changing terminals, and going through security again. The terminals can be far apart, and CDGs Passport Control can resemble a zoo at times. Frankfurt can be more efficient, but agree with others who say it's huge - it can be a VERY long walk. Amsterdam seems well-arranged and it's a pleasant place to make a connection each time we've been there. Last time we changed in Munich was over 5 years ago and I can't remember much about it...
And, don't forget - to add insult to injury, you usually go through another security line to enter your gate for US flights leaving from Europe.