Mr Bryson urged the delegation led by Congressman Richard Neal to open their minds and be prepared to hear the loyalist case against the post-Brexit deal which all unionist parties oppose.
In a direct message to Mr Neal and his fellow Congress members, Mr Bryson said: “The US and EU joint effort to force the implementation of the protocol demonstrates that these international actors have no understanding of the supposed balance that is meant to be at the heart of the Belfast Agreement that they purport to cherish, nor of the effect of the protocol itself.
“Calls to implement the protocol are calls for the subjugation of the Union and indeed unionists in Northern Ireland. That the international community is rallied behind a demand to ostracise, oppress and disenfranchise an entire community in Northern Ireland is quite remarkable.”
He continued: “Unionism/loyalism is under siege and we see this manifesting itself by the international pressure being applied, alongside propaganda – often dressed up as commentary or academia – being pushed regularly by partisan activists, some of whom are funded by EU projects.
“I am deeply concerned about the levels of anger and frustration in unionist but particularly loyalist communities. When you demand a community to be treated as second-class citizens and ignore all reasonable concerns, then you create a dangerous vacuum.
“I think people really need to listen very carefully to political unionism and representatives from the loyalist community. I cannot emphasise enough the level of concern I have at the anger which is at seething point among many young loyalists.”
Mr Bryson claimed that “international actors, particularly from the US, are inflaming tensions in an unprecedented way”.
He added: “I would call on the US delegation to come to grassroots unionist and loyalist communities, engage with us and at least listen to our concerns. This is a matter of the utmost urgency. Will they do so and demonstrate that loyalist concerns have currency?”