[HenryBemis]

Hey, (almost) everyone on Star Trek speaks english, with an American accent (apart this perfect human being called Jean Luc Piccard!!)(or with slight Russian accent). Even the Ferenghi!

That should have made it clear for you :)

[ComputerGuru]

They actually don’t. It’s explained in several TNG episodes as being a facade created by the “universal translator” plot device.

[dragonwriter]

> It’s explained in several TNG episodes

And TOS, for that matter.

[jcranmer]

Actually, the accent is more Polish than Russian (or so I've heard).