Yes, you can hire someone on Fiverr to build a Shopify store for you that is fully functional in Nigeria and set up to sell to customers in the United States. Shopify is a popular e-commerce platform that allows you to create online stores and sell products to customers worldwide. Here are the steps you can follow:

1. Hire a Shopify Expert on Fiverr:
- You can find experienced Shopify experts on Fiverr who can help you set up your store. Look for freelancers who have good reviews and a strong portfolio of successful Shopify projects.

2. Provide Specific Requirements:
- Clearly communicate your requirements to the freelancer. Specify that you want your store to be set up to sell to customers in the United States. This includes configuring currency, shipping options, and payment gateways that cater to the U.S. market.

3. Customize Your Store:
- Work with the Shopify expert to customize the look and feel of your store to match your brand and products. Ensure the store is user-friendly and visually appealing.

4. Product Listing and Inventory:
- Provide the freelancer with product details, images, and prices for the products you want to sell. They will help you set up product listings and manage inventory.

5. Payment and Shipping Settings:
- Ensure that the payment gateways are configured to accept U.S. payments, and set up shipping options that are relevant to the United States. This includes setting shipping rates, delivery times, and international shipping if needed.

6. Legal and Tax Considerations:
- Be aware of the legal and tax implications of selling to the United States from Nigeria. It's important to understand U.S. tax regulations, customs requirements, and any necessary permits or licenses.

7. Marketing and SEO:
- Work with the freelancer to optimize your store for search engines and set up marketing strategies to reach your target audience in the U.S. This includes keyword research, content creation, and social media integration.

8. Testing and Launch:
- Before the store goes live, thoroughly test it to ensure that everything is working correctly, from the shopping cart to checkout. Make sure that payment processing is smooth and that your customers can access their orders and receive confirmations.

9. Ongoing Support:
- Consider the need for ongoing support and maintenance. You may need assistance with updates, product additions, or troubleshooting issues that may arise.

When hiring someone on Fiverr or any freelance platform, it's important to communicate your specific needs clearly and establish a good working relationship. Also, be mindful of the budget, as costs can vary based on the complexity of the Shopify store and the level of customization required.