I have three devices that have micro USB to AC leads
A Phone, Tablet and a WiFi dongle
They are all 5.0Volts

But they have different amps: 550ma, 1.0amps and 2amps.

I don't want to carry three chargers.

So the question is:
Can I use the 2amp plug for the device that wants 550ma?
(without causing damage)

Yes you can. all USB is 5V. computer ports are up to 500mA

and various chargers are different currents. i think my tablet has a 3A charger, but it up to 3A rather than specifically 3A

but the charger will supply whichever is the maximum of it's power or that the device is requesting. no damage is caused either way. so you can use any. but obviously it makes sense to carry the largest one as it will be able to charge the device that requests the most current the fastest.

Thank you, Flagpole.