There were no real British interests involved in the boundaries of the Czech state in 1938 as there are no US real interests in the frontiers of Ukeland today. Let the Euros fight it out among themselves.
And you highlight exactly WHY the USA needs to be involved to push back Putin's invasion of Ukraine
1938 and the Sudentenland may not have had "real British interests involved" - but the war that occured 2 years later most definitely DID have British interests at heart
if the British and French had stopped hitler in 1938, they would not have had the tremendous loss of life and money in 1940 to 1945
Similarly, the USA is being smart by sending surplus weaponry to Ukraine to fight the war to push back Putin and prevent a wider war that would be detrimental to the USA