I'm not sure that the accent is neurological when singing. I think it's bio-mechanical.Def agree. When I sing French I find the placement of my tongue and vowels different from German, and Italian is def more forward. It's most interesting when I sing an English song. Tbh, when I sing pop I know my singing sounds different than when I sing 'classical' English-language songs. I think it's neat how our brain works like that and language is so different.
Regular speaking accents are in the brain though.