United States of America

a google search berthoud colorado sunflowers gives a lot of interesting results!

even one at pinterest that reads "Berthoud, Colorado we lived 3 miles from this picture. We would park like everyone else all alone the road to get pictures of these sunflowers...You can see Longs Peak and Mount Meeker." by ✿✿⊱JoAnn McBride

Sunflower field, Berthoud, Colorado, USA

(the SV i posted presents the very same orientation of the mounts)

copy paste of the description for the record:
Where's this sunflower field, and mountain in the background, in Loveland, Colorado? From external link

reddit says too:
- Is that Long’s Peak in the background?
- Yep haha.

that's a start