"But still, EU keeps threatening one."

Parrot.

"Ireland can not make such a commitment because it is not independent."

We are also not independent. Now here's a basic lesson for you, Keith. Are you listening? Good!

Ahem:

A "border" is a thingie with a country on one side and another country on the other side. When both those countries are democracies at peace with each other, they have an equal interest in deciding what happens at that border. When one or both of those countries are part of a larger bloc that has customs arrangements agreed on both sides, then the arrangement can change only if BOTH countries, with the blessing of the larger trading bloc, agree, or if they BOTH leave the bloc. But the larger trading bloc CAN'T BE BLAMED (or accused of issuing threats) if all it does is remind a country wishing to leave of its rules, which have to be maintained in the interests of consistency and fair play among all the countries in the bloc.   It's one hundred percent the doing of the leaving country if border arrangements thereby become problematical. The EU is pointing out the issue that the UK has brought about and is perfectly correct in insisting that its customs rules are not stretched at the whim of one country out of 28.

Hope this helps.