Can you fly to Europe from the US without a return ticket but with an on-going ticket to another country in Europe?
Of course. You don't even need that second ticket.
you may find your one way ticket costs as much and possibly more than a round trip ticket.
Just call some airlines and ask what your options are? We fly American Airlines, but they put us on British Air sometimes to London and then onto Zurich.
Check the price of one way vs round trip...they may be about the same....no one has told me why this should be!!!