In American football, a touchdown is worth six points.

Literal

American-football [at-で] touchdown [topic-は] 6-points become.

アメフト is the clipped loanword for アメリカンフットボール. タッチダウン and 6点 are straightforward. ~になる 'becomes / is worth' presents the point value as a natural outcome. A simple, factual sports-knowledge sentence.