Are there any regulations or guidelines that I need to follow to ensure that my shipping process is sustainable?

The USA has a number of regulations regarding sustainability, but most of them won't concern you as a Shopify seller. These regulations are built around the management of toxic chemicals and solid waste disposal.

That said, the Resource Conservation and Recovery Act (RCRA) provides guidelines on waste disposal while the Environmental Protection Agency (EPA) Initiatives provide resources for business to become more sustainable.

There are no regulations on eco-friendly packaging, however, there are multiple guidelines on how to reduce the carbon footprint of your packaging materials.