Most intro phonology classes discuss the fact that English /t,d/ are often flapped as the sound [ɾ] (often transcribed as [D]) which is actually the same as Spanish single “r” [ɾ].
For instance
atom /ætəm/ = [æɾəm]
Nevada /nevadə/ = [nevaɾə]
Spanish
pero ‘but’ = [peɾo]
manera ‘manner’ = [maneɾa]
In theory, an English speaker could confuse Spanish “r” and “d”, but in practice English speakers seem to be able to distinguish “d” and “r” (even the Spanish ones) except in some very rare cases.
The one time I experienced a “d/r” confusion from the TV show Roswell which featured a character named Nasedo But for years, I thought his name was Nasero.
I think this word was confusing because it fit the structure of both English and Spanish, and I probably know enough Spanish to think it was an /r/ (the story did take place in New Mexico). In most other cases (e.g. atom, there are other cues (such as the first vowel) to indicate it is English and not Spanish, so an English speaker interprets [ɾ] as either /t,d/.
I also suspect that there could be additional acoustic cues to help Americans distinguish English flap /t,d/ from Spanish flap /r/ … but maybe I’m just seeing spelled out words too.