Why does Gus Fring speak bad Spanish but good English?

Why does Gus Fring speak bad Spanish (with the accent of a stereotypical bad beginning American student) but good (perfectly American accented) English?

The out-of-universe explanation would be that the actor playing this character (Giancarlo Esposito) is American.

But I was wondering whether there's any plausible in-universe explanation?

Back story according to Fandom:

He claims to be from Chile, and is sometimes referred to by cartel members as "The Chilean", but it is unclear whether or not he was born there as no records of his life exist prior to 1986 ... Sometime during the 1980s, Gus fled Chile and in 1986 settled in Mexico ... Soon after, Gus emigrated to the United States and expanded his restaurant business.

Could it be that he actually grew up in the US?

The actor probably just couldn't do a good accent.

Giancarlo Esposito was born in Denmark and lived in Italy and New York when he was growing up. His father is Italian and his mother is American. I find no indication that he ever learned to speak Spanish well, and Valorum in the comments provides evidence he does not speak Spanish at all.

Don Eladio and Hector Salamanca call Fring "el Chileno" (the Chilean) in S4E8 ("Hermanos"), and Eladio later tells Fring that he spares his life only because "he knows who he really is." At no point does Eladio, Hector, or any other Spanish speaking character comment on his accent, suggesting that his Spanish was intended to be solid and the show runners knew most Americans would not notice, or mind.

Fring himself claims to be Chilean, though there is one hole in this story. In S4E6 ("Pinata) Fring tells a story about trapping a Coati as a child. Coati are found throughout most of Central and South America, but are not indigenous to Chile so is story is unlikely to have taken place there. If we accept his story as true, then he likely grew up somewhere in South or Central America, where coati live. He either later moved to Chile and became noteworthy somehow, or used that as a cover story to hide his real identity and Don Eladio only plays along in calling him the Chilean.