What was the significance of Winston Churchill's speech in 1946 in Fulton, Missouri?

Is that the famous Iron Curtain speech?

http://en.wikipedia.org/wiki/Fulton%2C_Missouri

Yes -- Iron Curtain speech.

=)

Would it be that in the "Iron Curtain speech" Winston Churchill drew attention to the fundamental split in Europe between the Eastern Bloc and the West, though at that stage (March 1946) there were no formal alliances?

Yes, You're right.