Because the power is applied through the chain and sprocket, power is typically limited to around 250–500 watts to protect against fast wear on the drivetrain. An electric mid-drive combined with an internal gear hub at the back hub may require care due to the lack of a clutch mechanism to soften the shock to the gears at the moment of re-engagement. A continuously variable transmission or a fully automatic internal gear hub may reduce the shocks due to the viscosity of oils used for liquid coupling instead of the mechanical couplings of the conventional internal gear hubs.
So instead of giving US companies breathing room to manufacture their own e-bikes, the tariffs are largely just hurting the US electric bicycle industry by preventing it from importing and selling affordable e-bikes, without solving the underlying reasons causing US e-bike companies to choose not to manufacture their e-bikes in the US in the first place.
Electric bikes are here in a big way. Liberated from some of the normal constraints of standard bike design like weight and gearing, e-bike design has exploded; if you can imagine it, someone has built it. From cargo bikes to city bikes, messenger bikes to mountain bikes, road bikes, and even beach cruisers, there is something for everyone. The beauty of e-bikes is they make the joy of cycling accessible to so many people in so many ways.