What is the theme of "Bilingual" by Rhina P. Espaillat, and how does it connect it to "Girl" by Jamaica Kincaid?

A primary theme of Espaillat's poem "Bilingual/Bilingüe" is straddling two cultures creates conflicts. This is certainly the case for the speaker's father, who wants the speaker to be able to navigate the English-speaking world well, but still remember her culture and heritage by speaking Spanish at home. Even as a famous writer, the speaker says of her father:

"even when, 
proud (orgulloso) of his daughter’s pen, 

he stood outside mis versos, half in fear 
of words he loved but wanted not to hear" (lines 15-18)

The speaker is saying that her father is conflicted between pride of her talent at writing poetry and dismay at the way she has blended Spanish and English, and the two cultures these represent. The speaker herself is conflicted as well, describing reading English in the house to practice, against the father's wishes:

"I hoarded secret syllables I read 

until my tongue (mi lengua) learned to run 

where his stumbled" (lines 12-14).

The speaker understands the importance of learning English well, but in order to do so, she needs to break her father's rule. Also, it separates her from him in a meaningful way; she can speak English well, while he cannot. 

The theme of straddling two cultures creates conflicts is relevant in Kincaid's "Girl" as well. "Girl" takes place in the Caribbean Islands, where European colonization has a firm influence. In the mother's monologue of advice to her daughter, she teaches her ways in which her native Antiguan culture needs to stay separate from her British culture:

"Is it true that you sing benna in Sunday School? [...] don't sing benna in Sunday school"

Benna is a calypso-like style of music that was used as a way to spread scandalous information and rumors, and often also had a sexual double meaning. It definitely wasn't appropriate for a religious setting and probably not for the ears of the white folks who would presumably be presiding over Sunday school. This quote shows the mother encouraging the girl to keep these cultures separate. 

There could also be a conflict through the girl's faith. The girl goes to Sunday school, but the mother also teaches her the traditional religion Obeah, saying things like

"Don't throw stones at blackbirds because it might not be a blackbird at all,"

which demonstrate the Obeah beliefs she still holds. The perils of navigating two cultures, especially two with an uneven power dynamic, create some conflict and confusion in the adolescent girl, as well as in the mother, who is exasperated with her daughter and fearful of her failure.