How to increase speed on X-Treme Ebike

Hi, everyone!
I got X-Treme Alpine Trails bike https://electricbicycle.com/products/24-volt-electric-bicycles/alpine-trails#/2

It can reach the speed of 15-16 mph without a pedal assist, though the promised speed is up to 20 mph.
I figured out the bike wasn't modified for U.S speed limit regulations.

I wonder if anybody knows how can I increase the speed?
I know it's very easy to do in Ancheer bikes by disconnecting a white wire in a controller box but I couldn't find such a wire in my bike.

Thanks!

Can you post so photos of the controller? That would give us a better idea what you are working with. It looks like the connections may be enclosed under the battery.