Does Airmac extreme(Japanese version) works fine in the US?

I got a airmac extreme right now.

On setting

I only have a country choice with Japan.

I'm not sure but I sometimes have connectivity problems.

Sometimes internet freeze and so on,

Is it the country problem? Or just internet router(ATT UVERSE) problem?

I'm just wondering if I connect US version.

That would be better connectivity or not..