It's up to the DM.
Notably, a square area of effect is not defined in the Player's Handbook. Most area of effect shapes are given clear and precise definitions for their points of origin. We have nothing for the square.
So we have two possible DM rulings.
1. The point of origin is the center.
If the DM rules that the point of origin is the center of a square, then the furthest our entangle area can effect is 100 feet away. This ruling would be consistent with how spheres work.
This would bring entangle in line with the wording of the spell grease, which says:
Slick grease covers the ground in a 10-foot square centered on a point within range
2. The point origin can be any part of the square.
Since entangle lacks the "centered" language found in grease, it would be reasonable to rule that the point of origin can be any part of the square. If this is the case, then our entangle can affect area up to 110 feet away.
Either way, we know we can affect some area past the 90 foot range, because of the spellcasting rule that says:
Once a spell is cast, its effects aren't limited by its range, unless the spell's description says otherwise.