Guess it depends on what the meaning of "we" is.
The French army at the time was sizable and well equipped.
And the English navy was second to none.
Hitchens is very good at cataloging the effect of Leftism on British culture, but he does have weird views. Hitler most certainly could have been stopped early on as the German army was much weaker than Hitler’s confidence made it look. The German Generals didn’t want war and warned hitler repeatedly that they were too weak to withstand a concerted effort by the Allies.
Nope. If there had been war in 1938, Germany would have lost. As you said, the French army was formidable. And the main reason Hitler wanted the Sudetenland is that it was a well-fortified mountainous region. If the Czechs hadn't been betrayed, they could have held back the Germans.
And suppose the Poles got involved. They had a decent army as well. Hitler would have been bloodied, and then overthrown by a military coup.
In 1938, either Hitler or Stalin could have beaten us, but fortunately for us, they fought each other over who would do it, and it left both of them too weak to finish the job.