WIth a speed limit of 90 km/h, the difference between 120 kW and 250 kW is actually quite small - at least until you get your tow bar.
For a LR RWD, the effective traveling speed when actually driving 90 km/h and when charging at 120 kW is 83 km/h, and if the charging power is increased to 250 kW, the effective traveling speed goes up to 87 km/h. (The difference up to the 90 km/h is basically cut in half by doubling the charging power).
So while I hope that Iceland (and everyone else) get v3 Supercharging, places with low speed limits would suffer the least from not getting them. This would include Norway, that has rather few stretches with highways.
It follows that Germany would benefit the most from v3.
If the actual driving speed for a LR RWD is 180 km/h, then the effective traveling speed is 123 km/h with 120 kW charging. Increasing the charging power to 250 kW increases the effective traveling speed to 148 km/h, so a significant difference.
For higher driving speeds the difference in charging power has greater effect.
With 120 kW charging a driving speed of 192 km/h minimizes the sum of driving and charging (for an effective traveling speed still at 123 km/h), while with 250 kW charging the LR RWD would have to drive at full speed (around 235 km/h) to minimize the sum of the driving and charging time (for an effective traveling speed of 160 km/h).
Since Tesla seems to itch to give the Tesla smack down to especially the Germans and their ICEs I would not be surprised to see the v3 deployed liberally along the Autobahn. That will really hurt the Germans, to be overtaken by Teslas on the very Autobahn that they have kept speed limit free exactly to provide a market for their expensive German cars.