It's in a written document from the US and on their trade website. Or are you intentionally in denial to facts?
If we accept lower US standards and imports then our exports which are primarily to the EU for livestock will suffer as already foreign buyers have cancelled their orders for UK meat. Farming will suffer.
https://www.farminguk.com/news/Overseas-buyers-cancel-British-meat-orders-due-to-Brexit_51451.html
If we do not accept lower standards then we won't get the US trade deal so we will be back where we started but now our produce costs more due to tariffs. Farming will suffer.
Yet you still want Brexit to wreck the economy.
I see the NFU are campaigning for govermnent assurances that food and agricultural standards will be sacrosanct. They want the standards to be unbreakable so that US imports cant undercut UK production and force farmers to lower standards.