Configure the three different product types to make sure that you are using the right attribute values for the different product types. 
We recommend to only export products which can be bought in your store as configurable products or a non-indivual-visible simple product in a grouped or bundled product can't be bought by itself.

For the official information about the Bundled Product specification.
Click here.

Setting overview based on the Google Shopping Magento 2 extension.

Configurable Products
For configurable products, we recommend to only add the simple products to the configuration as a ‘configurable product’ by itself cannot be purchased. Choose the attribute(s) that you want to use from the parent relation configurable product.

Use Configurable/Simple Products
Recommended: Only Linked Simple Products. Selecting this option will export linked simple products that are part of a configurable product. This option is recommended so that the unique product variants are exported to the Google Shopping Feed.

Use Parent URL for Simples
Recommended: Yes, with Auto-Link. In this way the URL will be automatically link to the correct simple product on the configurable product landing page.

Use Parent Image for Simples
Recommended: Only if Empty. Selecting this option will export the parent image which will be used if there is no image available for a simple product.

Use Parent Data for Simples NameDescriptionBrandGtinMpnConditionColorGenderMaterialPatternSizeSize TypeSize SystemWeight
Select the attributes that you want to use from the parent configurable product. It is not recommended to select the attributes that need to be unique for the simples, such as GTIN and Color.

Use Fallback only on Non Visible Simples
Recommended: Yes. In this way you only use the logic for the attribute fallback and relations on simples with the visibility "Not Visible Individually". Simples that are visible in the catalog are treated als "normal" simple products without relations.

Bundle Products
For Bundle Products, we recommend to only add the Bundle product by itself as this is the item that can be purchased.
Recommended: Only Bundle Product. Selecting this option will export the bundle product by itself to the Google Shopping Feed.

Use Parent URL for Simples
Recommended: Yes. Selecting this option will export the URL that links directly to the Bundle Product.

Use Parent Image for Simples
Recommended: Only if Empty. Selecting this option will export the parent image which will be used if there is no image available for a simple product

Use Parent Data for Simples NameDescriptionBrandGtinMpnConditionColorGenderMaterialPatternSizeSize TypeSize SystemWeight
Select the attributes that you want to use from the parent bundle product. It is not recommended to select the attributes that need to be unique for the simples, such as GTIN and Color.

Use Fallback only on Non Visible Simples
Recommended: Yes. This selecting will use the logic for the attribute fallback and relations on simples with the visibility "Not Visible Individually". Simples that are visible in the catalog are treated as "normal" simple products without relations.

Grouped Products
For Group Products, we recommend to only add the Grouped Product by itself as that is the product that can be purchased.
Recommended: Only Grouped Product. Selecting this option will export the bundle product by itself to the Google Shopping Feed.

Use Parent URL for Simples
Recommended: Yes. Selecting this option will export the URL that links directly to the Bundle Product.

Use Parent Image for Simples
Recommended: Only if Empty. Selecting this option will export the parent image which will be used if there is no image available for a simple product

Use Parent Data for Simples NameDescriptionBrandGtinMpnConditionColorGenderMaterialPatternSizeSize TypeSize SystemWeight
Select the attributes that you want to use from the parent grouped product. It is not recommended to select the attributes that need to be unique for the simples, such as GTIN and Color.

Use Fallback only on Non Visible Simples
Recommended: Yes. This selecting will use the logic for the attribute fallback and relations on simples with the visibility "Not Visible Individually". Simples that are visible in the catalog are treated as "normal" simple products without relations.