This is the 19402nd most frequent Korean word.
애국심을
Patriotism.
The word "애국심을" is used here as the object of the verb "가지고 행동하는", meaning to act with patriotism.
애국심을 가지고 행동하는 것은 중요합니다.
Acting with patriotism is important.
In this sentence, "애국심을" serves as the object of the verb "가르치는", which means to teach patriotism to someone.
어린이들에게 애국심을 가르치는 것이 필요합니다.
It is necessary to teach children patriotism.
Here "애국심을" is the object of "표현하기 위해", indicating expressing patriotism as the motivation for the action.