We don't have invitation letter templates for travelers coming to USA for business purposes or other purposes. The US embassy requirements of invitation letter templates for visitors to USA can vary from country to country. Please check the website of US Embassy or US consulate in your country to find the template of invitation letter required by them to process your US visa.
We have a generic invitation letter that is used by our clients to process visas with various embassies and consulates in USA. You can use it for reference purposes by clicking here.