According to page 2 of IRS Publication 555 Community Property, you would only complete Form 8958 if you were domiciled in a community property state. Community property laws only apply to those who are actually domiciled in the state:
The law of the state where you are domiciled will determine if you have community property, community income, or both. If you and your spouse (or your registered domestic partner) have different domiciles, check the laws of each to see if you have community property, community income, or both.
You have only one domicile even if you have more than one home. Your domicile is a permanent legal home that you intend to use for an indefinite or unlimited period, and to which, when absent, you intend to return. The question of your domicile is mainly a matter of your intention as indicated by your actions. You must be able to show that you intend a given place or state to be your permanent home. If you move into or out of a community property state during the year, you may or may not have community income.
Factors considered in determining domicile include:
Amount of time spent. The amount of time spent in one place doesn't always explain the difference between home and domicile. A temporary home or residence may continue for months or years while a domicile may be established the first moment you occupy the property. Your intent is the determining factor in proving where you have your domicile.
Note. When this publication refers to where you live, it means your domicile.