Hello,
1.
Following each step of the "Payment methods" section of the FAQ will probably help you :
Sorry, here is the link to the FAQ :
www.hikashop.com/support/faq.html#paym
Restricting all your shipping methods or payment methods to a zone different than "US" will do the job. " ← How To Set ?
How to limit?
Which plugin?
By Creating a custom shipping zone via "Hikashop->System->Zones", adding in it every country but not US, and then by using that custom shipping zone through the "Zone" option of your payment/shipping method configuration page.
Setting the US
Transport and can not buy
I didn't really undersood, can you give me more detail about it ?