In order for moderation through institutional inclusion to take full hold, it was necessary for the US to act as a powerful external broker throughout the negotiations of the Belfast Agreement and during the consolidation of republican moderation. Just as consociational theory needed to be tailored for the ethno-national context by acknowledging the role of international actors, similarly the moderation of republicanism required a powerful external broker. Like many external interventions, it was short and targeted, not of relevance in the early stages of republican moderation and only mattered during the formal peace process phase and its implementation.

The role of the US in enabling republican moderation through institutional contact was very specific. It provided a series of credible guarantees to republicans that their interests would be protected and given fair representation when entering a bargain with the more powerful British state. As Walter argues:

In this way, an international intervention can help overcome the reluctance of adversaries to commit to moderation where there is a history of hostility engendering suspicion of the adversaries’ motives. The US provided a series of incentives and disincentives that encouraged republicanism to increase their engagement with the peace process. Combined, these factors led to greater republican inclusion within the ruling institutions. What is more, although certain sections of Irish-America flirted with promoting radical republican views in the 1970s, by the time the US government embarked upon its role as guarantor it had firmly embraced a constitutional nationalist understanding of how the conflict should be resolved. That is not to say that it was an active promoter of Irish unity, but given that it accepted Irish unity as a legitimate political aspiration it strongly promoted that this needed to be pursued through the principle of consent and certainly not through armed struggle.