I've found in the FAQ that you need to remove the other countries from the variations, I did and I've removed several variations.
But how do I know which ID variation I should remove for for instance USA - White.
You have to remove variations from the countries that you do not want to ship from. As I know in your screenshot you have to remove all variations except Ships from USA. You have to keep 429 only.
Next I have been still working around on how to hide it on frontend from the customers. There is a thread about it on the forum but could not make it work for me. It is a good idea to hide it with CSS code but make it selected. Of I find it I will reply. Have a nice day.