If I order snacks from another country can they send me something with US "banned" ingredients?

Depends on what the “ban” rules say.

Some bans are just for retailers selling in the jurisdiction the law applies to, for example.

Yes, they can, because hardly anyone is checking.

The US hasn’t banned HFCS. Consumption in the US has remained steady for the past 10 years. maybe you were just making up an example

LOL @smudges

> Just using a random example, obviously this is not reality.

Yes, it was a made up example lol

Generally speaking, they can send the aforementioned snax.

Per your example, HFCS doesn’t present an immediate danger to virtually anyone, and at worst, it will probably present a long-term health threat only to the consumer.

Legality is up to the sender. The DEA, FDA, or ATF agents will not be at your door.
Realistically of course you can.

Actual example from ~20 years ago:

Absinthe was generally illegal to sell in the USA. Not illegal in France. People in the US can/did order it from vendors in France.

They’re not supposed to sell products to America with USDA or FDA banned ingredients.
But realistically speaking, you can literally order coca leaf from Brazil, and odds are greater than 99% that you’ll receive it, no problem.