it’s included, you don’t see the price without sales tax, therefore you don’t truelly see the cost of the product versus the cost of the taxation.
Casting my eye over the invoices on my desk from wiggle, CRC and Amazon I see that they all have itemised prices showing cost before and after VAT.
So it’s not quite as stealth as you suggest.
And as others pointed out, the US only makes a point of highlighting that one sales tax.
They (obviously) don’t itemise all the other background taxes which still have an effect on the cost of an item (e.g. corporation tax, business rates, import duties, fuel tax, etc etc).