The United States Customs strictly limits the types and quantities of items in imported packages. Some of these regulations include:

(1) Prohibited items for import

The United States Customs prohibits the import of certain items, including but not limited to:

1. Controlled drugs, prohibited drugs, and drugs containing toxins

2. Some products, such as revolutionary military products, false currency, sex gambling products, etc

3. Arms, weapons, and items related to national security

4. Animal products and exotic species

5. Counterfeit brand products and pirated products

(2) Restricted imports

In addition, the import of some items is also restricted, including:

1. Food and drugs require FDA approval

2. Textiles and clothing need to be approved by the Trade Supervision Bureau

3. Electronic equipment and electronic products shall pass the safety certification of FCC (Federal Communications Commission) and UL (American Safety Laboratory)

4. Some souvenirs, artworks, etc. need to be certified by relevant compliance departments

The above is only an example, and specific regulations can be referred to the US Customs website or relevant personnel of consulting logistics companies.