[M language] Transform column type to datetime with 2 string formats?

Hi all,

I have a column timestamp as string. In this column we can find two format of datetime dd/mm/yyyy hh:mm:ss (European datetime) and mm/dd/yyyy hh:mm:ss AM/PM (USA datetime).

I want to convert this column data type to datetime, but I can't with two string formats.

I tried to to make a custom column with an IF statement like this:

let
    Source = DocumentDB.Contents("https://avabot.documents.azure.com:443/"),
    history = Source{[id="history"]}[Collections],
    history_MessageHistoryItem = history{[db_id="history",id="MessageHistoryItem"]}[Documents],
    #"Expanded Document" = Table.ExpandRecordColumn(history_MessageHistoryItem, "Document", {"conversationid", "timestamp", "text", "id", "_rid", "_self", "_etag", "_attachments", "_ts", "sender", "recipient"}, {"Document.conversationid", "Document.timestamp", "Document.text", "Document.id", "Document._rid", "Document._self", "Document._etag", "Document._attachments", "Document._ts", "Document.sender", "Document.recipient"}),
    #"Convert Date" = Table.AddColumn(#"Expanded Document", "Custom Timestamp", each if Text.Contains([Document.timestamp], " AM") or Text.Contains([Document.timestamp], " PM") then Table.TransformColumnTypes(#"Expanded Document",{"Document.timestamp", type datetime},"en-US") else Table.TransformColumnTypes(#"Expanded Document",{"Document.timestamp", type datetime},null))
in
    #"Convert Date"

But i get a table in each rows, but the correct TransformColumnTypes is done for the row:

Then I tried to stock the string format in the custom column to use it in the transform column types statement:

let
    Source = DocumentDB.Contents("https://avabot.documents.azure.com:443/"),
    history = Source{[id="history"]}[Collections],
    history_MessageHistoryItem = history{[db_id="history",id="MessageHistoryItem"]}[Documents],
    #"Expanded Document" = Table.ExpandRecordColumn(history_MessageHistoryItem, "Document", {"conversationid", "timestamp", "text", "id", "_rid", "_self", "_etag", "_attachments", "_ts", "sender", "recipient"}, {"Document.conversationid", "Document.timestamp", "Document.text", "Document.id", "Document._rid", "Document._self", "Document._etag", "Document._attachments", "Document._ts", "Document.sender", "Document.recipient"}),
	#"Convert Date" = Table.AddColumn(#"Expanded Document", "Datetime Format", each if Text.Contains([Document.timestamp], " AM") or Text.Contains([Document.timestamp], " PM") then "en-US" else null),
	#"Changed Type" = Table.TransformColumnTypes(#"Convert Date",{"Document.timestamp", type datetime},[Datetime Format])
	
in
    #"Changed Type"

But i get this error: Expression.Error: There is an unknown identifier. Did you use the [field] shorthand for a _[field] outside of an 'each' expression?

I'm running out of idea, so if someone could help me with this issue I'll be very thankful to him.

Kind regards.