So you can’t get the affidavit from the US embassy anymore- where do you go??

Trying to get married at city hall and presented them with the letter from the embassy about how they don’t do the affidavits for getting married anymore. City hall didn’t care and told us to get one anyways from a US notary. If I can’t get it from the embassy that means I have to go back to America to get it ? They also told my fiancé they want my birth certificate but didn’t specify if it had to be the official/original or a copy. This also was the main city hall for my area and not a small offshoot branch office.

I do go back to America for Christmas and new years so I could in theory get it then but I wanted to switch to the spouse visa sooner- before things will likely pick up with the new school year and a lot of the student and teacher visa applications coming in.