What are the concerns about the meeting between Russia and the United States excluding Ukraine's President Zelensky?

The meeting raises historical concerns among Europeans and Washington officials about potential parallels to 1938, when Britain and France negotiated with Hitler over Czechoslovakia without its input, leading to World War II. The Russians appear pleased with achieving Putin's goal of dealing directly with the US over Ukraine's head. Zelensky is particularly alarmed that a deal might be struck sacrificing Ukrainian territory, similar to how Czechoslovakia disappeared within a year after the 1938 Munich agreement. This exclusion has created anxiety about history potentially repeating itself through great powers making decisions affecting Ukraine without its participation.