Tax is not getting calculated correctly in the item level of Sales order

We are updating the Tax departure country(tkomk-aland) in Userexit : USEREXIT_PRICING_PREPARE_TKOMK based on decision points either with shipping plant country or Sales order company code country respectively . If the Tax departure country is "US", It need to calculate the US tax,But its not happeningcapture.png . DO we have any impact on Tax calculation based on Tax departure country . If we have any impact, At what point I need to make changes in the code to calculate the tax correctly. Kindly do the needful. Thanks in advance.