Copyright Protection for Foreign Photographers
All unpublished photos, regardless of the nationality of the photographer, are protected in the United States. Any photo that is protected by US copyright law can be registered, which includes works of foreign origin. Look at Short Form VA for registering photographs. In section 2 where it asks for your name and address, it also asks for your nationality or domicile (the country that you consider your "home"). It does not require that you be a US citizen.
If your photos are first published in the United States or in a country with which the US has a copyright treaty, they also are protected and may therefore be registered with the US Copyright Office. Also, if you are a citizen of or reside in a country that has a copyright treaty with the US, then you can register your photos with the US Copyright Office. See Circular 38a, International Copyright Relations of the United States, for the status of specific countries.
Once your register your images with the US Copyright Office, you will likely find it worth the time and effort to prosecute infringements that occur in the United States. So, foreign photographers, register your images in the US now!
Take my advice; get professional help.