@Puduhepa , US sourced earnings are incomes that come from US sources and are taxable by the USA --- wages for work performed at US tax home ( i.e. when the work function is done in the USA), self-employment income where again the tax home is USA; dis-regarded entity, like single member llc income where the the entity has a physical presence in the USA ( a mere registered name is not sufficient ); passive incomes like rental income from US real-estate, interest income from US banks, etc. etc. -- in all cases the common thread is tax home being US or the asset is located in the USA. Mere US customers paying for the product does not make the source as USA
US connected is usually income from businesses where the entity is US based for example dividend from stocks of US entities is US connected / sourced. Connected generally looks as "closer " connection. For example, if an employee of a German entity came to the USA and worked here for three months on installing and bringing "on-stream" machinery bought by an American entity from the German entity, this employee's earning while in the USA would not be US sourced ( work was done in the USA ) because the employee's tax home is Germany , his family lives in Germany, he intended to return to Germany at the end of his work stay, his bank is in Germany, his children go to school in Germany etc. etc. ----- i.e. he had a closer connection to Germany
Most of these sourcing conventions are based on Tax Treaty agreement -- and these are common for all US-X tax treaties.
VAT or sales taxes collected at point of sales is a tax on the consumer and therefore your "sales agent" like Amazon collect these fees and have nothing to do with your own income ( from sales ) or your entity's ( LLC ) income for US tax purposes.
As has been said before and what you have heard from the IRS, the income from your LLC is NOT US sourced/Connected. Thus I am at a loss to understand why you want to file a US tax return -- what are you trying to achieve ?
I do not believe I can help you more on this. Perhaps you should consider consulting a tax professional or an attorney familiar with international tax filing
stay safe
