We first think of the German delegates forming a single German block, denoted G, the French delegates forming a single French block F, and the Italian delegates forming a single Italian block I. Then there are $ 3!= 6 $ ways to arrange the three blocks in a row: $$\textbf{FGI, FIG, GFI, GIF, IFG, IGF}$$ Within each block, there are $ 6!$ ways to arrange the German delegates, $ 5!$ ways to arrange the French delegates, and $ 3!$ ways to arrange the Italian delegates. Therefore, there are $$ 3!\times 6!\times 5!\times 3!= 6 \times 720 \times 120 \times 6 = \boxed{3,\!110,\!400} $$ ways to seat all 14 delegates.