“미국도 별 수 없네”라는 생각을 단번에 뒤집어 버린 President Trump

You gotta be kidding me.
1) it doesn’t matter. 2) in this case, difference (singular) is more correct. 3) if you don’t believe me, google is your friend.

BTW, I welcome another English grammar flame war waged by crippled Konglish speakers.