The following scenarios assure the US advance:
(1) US win AND Italy win.
(2) US win by 5 or more AND the Czechs draw 2-2, or 3-3.
(3) US win by 4 or more AND the Czechs draw 1-1 or win 1-0, 2-1, 3-1, or 4-2.
(4) US win by 3 or more AND the Czechs win 2-0, 3-0, or 4-1.
(5) US win by 2 or more AND the Czechs win 4-0, or 5-1.
(6) US win by 1 or more AND the Czechs win 5-0.
In the following scenarios the US would have to draw lots to advance:
(1) US wins 2-1 AND the Czechs win 4-0.
(2) US wins 2-0 AND the Czechs win 3-0.
(3) US wins 3-0 AND the Czechs win 3-1.
(4) US wins 4-0 AND the Czechs win 3-2.
-A8
I think it's fair to say, we only have to consider (1) from your analysis above.