This is the 88th most frequent Italian word.
negli
"In the" (used with plural masculine nouns).
The word 'negli' is the contraction of 'in' and the plural masculine article 'gli', and it's used here to indicate location in a plural masculine place, 'Stati Uniti'.
Viviamo negli Stati Uniti.
We live in the United States.
Here, 'negli' combines 'in' with 'gli' to indicate a period of time described by the plural masculine phrase 'ultimi anni'.
Negli ultimi anni, molte cose sono cambiate.
In recent years, many things have changed.
In this sentence, 'negli' is used as 'in' plus 'gli', referring to a specific location described by the plural masculine noun 'scaffali'.