Who is my FA?
How would I know? But it doesn't matter: If your local youth club decides to host an officially sanctioned international tournament, they might go ask IFAB about what size to make the pitches. IFAB is going to tell them that if they meet the national FA guidelines, then they meet the IFAB guidelines. (Look at page 25 of the IFAB law book)
To be pedantic though, EUFA defines grassroots football as anything that is non-professional and non-elite, and since 2017 IFAB says that national FAs are free to make their own rules on pitch dimensions for grassroots football. So there is no contradiction - IFAB, EUFA and your FA are all in agreement :)