I agree that opposed landings are not easy, and that there would be problems with regard to supply.
The point is that Britain in 1938 was about as undefended as America at the time[/HILITE].
But you just told us that the US had the "military clout" to intervene meaningfully in a war between Czechoslovakia and Germany. Are you now conceding that you were mistaken about that? Additionally, please explain where your hypothetical 1938 German invasion force was going to embark, how it was going to reach Britain, and how it was going to land.
The 'heroic' British navy could only do so much against the Lufwaffe without air support.
I don't know why you put "heroic" in quotes. Are you questioning the RN's heroism during World War II? And exactly how do you think the Luftwaffe was going to attack British ships in 1938? No handwaving; be specific. Finally, what makes you think that the RN wouldn't have had air support in opposing a German landing in 1938?
Chamberlain was right to talk about "peace in our time" while he corrected deficiencies in the air force and the army.
Chamberlain actually made deep cuts to the Army's budget during the late 1930s. Fail.
It avoided a devastating bombing attack. I would have done the same thing in his shoes.
Your claim that Britain would have suffered a "devastating bombing attack" in 1938, or even 1939, has been repeatedly shown to be erroneous.