Peer approval schemes are usually implemented as trade efficiency measures. A one sided peer approval would make it easier to import, while not making it easier to export, causing a delta trade deficit.

Why is a trade deficit something to worry about? After all, my local grocery store buys nothing from me, but we both benefit from the exchange of goods and currency.

That how you end up with chlorinated chicken you'd never knowingly eat.

Obviously any authority that takes its job seriously makes decisions based on facts and not blind trust.

This isn't about trade efficiency though, it's about bypassing an inefficient bureaucracy by allowing for approval by a more efficient one as an option.

We have no intention of dropping our standards to US ones, but they are welcome to follow our lead. (Or don't! It's up to you, just don't make it our problem!)

That's a problem for the country with insufficient approval schemes to deal with, especially if they're also doing more work out of spite.

For a country which has a sufficient approval scheme, they lose little by choosing not to trusting an insufficient approval scheme.