Can a house be wired to American electrical standards in one room and European standards in the others?

Question

The house will have its own electical generator, not use local power supplies.

Answer 1

It may be possible, but in America we have a different frequency.

In Europe it is 50 hz

In America it is 60 hz.

60 hz. is better because you get more cycles per seconed.

Answer 2

Theoretically yes, but you will never get an electrical inspector, or fire marshal to sign off and approve the installation.  As you are "off the grid" you may not need to have an electrical inspector to come in and approve it, bit it is worth checking with your local building codes to see what they require.