The AC power cable plugs are different based on power voltages and type or shape of socket and plug as below images.
different AC power adapters
If you purchased some electric appliances from outside of US and it will not from US due to above reasons. And there will be two different solutions to use those appliances in US.
First, if the electric appliance is fixed to support 220V, then it will need to have 100V to 220V upscale transfer as below image. The appliance will be directly connect to below transfer to use at any time. This transfer solution is expensive way but there is no other simple ways since the appliance not supporting free voltage.
Use 220V appliance from transfer that 100V is the resource.
Second, if it is supporting the Free Voltages, it will need the simple adapter that can be easily plugged to existing 220V plug so that the power cable can be easily fit into to Socket in US. The Free Voltage can take from 100V to 250V and this should be clearly indicated near power cable area or user manual. So, you should make sure to read or identify whether it is supporting the Free Voltage or not before using this type of adapters.
Used AC 110V power plug adapter
And you can observer whether the power charger or adapter has a detachable power codes from the main body as below picture. Then, you can purchase the power cable that can be fit into US socket type.
replace power cable from 220V to 110V
You can also purchase the simple plug in adapter at the below site.