How can I resolve my merchant center approval issues related to checkout?

[Ctmph2022]

Hello, I am having a problem getting approved on merchant center. The problem is in my checkout (or so they say) 

I think I have a few possibilities of what it is. 

1) I don't have my payment options listed on checkout, and if this is the case how do I make sure that I have them listed exactly? 

2) I for some reason am not accepting ip addresses from other countries, I'm not shipping to other countries yet but I'm only delivering to the U.S, how do I ensure I'm accepting IP addresses internationally?

3) I don't have international availability for purchases in my shopify store, and if I don't already, how do I go about fixing this? 

Also, is it better to be able to ship out to the whole world? Or should I keep it US based? 

How complicated is it to set up shipping methods for international buyers and how do I convert the currencies from international to us dollar? I had trouble figuring out shipping methods for us as it is. So the proper guidance here would be great.