from the National Constitution Center:

from the National Constitution Center:

The conflict centered on the independent Republic of Texas, which opted to join the United States after establishing its independence from Mexico a decade earlier.

The new U.S. president, James K. Polk, also wanted Texas as part of the United States, and his predecessor, John Tyler, had a late change of heart and started the admission process before he left office. Polk and others saw the acquisition of Texas, California, Oregon, and other territories as part of the nation’s Manifest Destiny to spread democracy over the continent.

Cite this source: (NCC Staff, 2021)

Which quote from the text BEST helps explain a reason why the United States became involved in the Mexican-American War?

"The conflict centered on the independent Republic of Texas..."
"[Texas] opted to join the United States after establishing its independence from Mexico a decade earlier."
"Polk and others saw the acquisition of Texas, California, Oregon, and other territories as part of the nation’s Manifest Destiny to spread democracy over the continent."