Building a Green Wall explores the re-engagement of the Irish-American diaspora in influencing US policy toward Ireland and Northern Ireland in the aftermath of Brexit. Kimberly Cowell-Meyers and Carolyn Gallaher contend that the Irish diaspora in the United States had been mobilized during the Troubles and became engaged and supportive of the peace process in the 1990s. Once the Good Friday Agreement was signed and promised peace, however, many in the diaspora became less engaged in Irish and Northern Irish politics. Brexit reawakened the Irish community in America, as they feared the prospect of a hard border and what it might mean for the peace that had been achieved in 1998. Following the lead of the Irish government and its efforts to influence European negotiators responsible for concluding the Withdrawal Agreement of the United Kingdom from the European Union, the Irish-American lobby in the United States mobilized to prevent a return to the violence and promote an open border for trade.

The establishment of a seamless north–south border in Ireland had been an important achievement for Irish nationalists and republicans. While not immediately achieving the long-term aspiration of a thirty-two-county republic, the geographic and economic integration of Ireland north and south after the Good Friday Agreement ended searches and border stops that had separated the island since partition in the 1920s. Cowell-Meyers and Gallaher skillfully build an argument that numerous Irish-Americans, and especially the Ad Hoc Committee to Protect the Good Friday Agreement, played a purposeful and effective role in convincing American diplomats to support the Irish and EU efforts to prevent a hard border and a return to violence that such a border would likely have brought. By focusing on Irish-America, Building a Green Wall recognizes the network of individuals in the Irish government and diplomatic corps, leaders in Northern Ireland, and British and EU negotiators over Northern Ireland’s status after a withdrawal agreement. Indeed, one of the virtues of the book is that it does not see Irish America in isolation but recognizes how this diasporic lobby understood its role in the complex web of actors who were involved with the post-Brexit fate of Northern Ireland.

While US policy remained generally in favor of maintaining good relations with its historic ally, Great Britain, Cowell-Meyers, and Gallaher contend that Brexit put a strain on this close relationship. First, the US generally sided with Ireland and the EU in seeking to prevent a hard border, but Boris Johnson’s negotiating posture and willingness to threaten Britain’s commitments undermined US support for the British position during the Brexit negotiations. The arrival of a very Irish-American president, Joe Biden, in 2021 further tipped American influence in favor of the prevention of a hard border and the preservation of the peace achieved with the Good Friday Agreement.

Building a Green Wall’s research was based primarily on a review of public statements and documents and on interviews with leaders on both sides of the Atlantic. To understand the role of the Irish-American lobby, Cowell-Meyers and Gallaher interviewed twenty-three members of this group. Some serve or had served in Congress. Others had served in diplomatic roles for the US government. They represented a wide range of roles and views within the Irish-American diaspora. In addition, the authors interviewed two Irish leaders involved in negotiations after Brexit as well as nine individuals from government, business, and academia in Northern Ireland. By seeking to have Irish and British leaders weigh in on the American role in the negotiations after 2016, the authors were able to corroborate the Irish-American influence on the eventual Withdrawal Agreement and the prevention of a hard border in Ireland.

One of the most important findings of the book is the point it makes about the dynamism of ethnic lobbies. Rather than seeing ethnic lobbies as having a fixed role and influence in the foreign policy–making process, the resurgence of Irish America in the aftermath of Brexit suggests that their influence shifts based on external events, especially important events in the diaspora’s ancestral nation. This is particularly likely in a group whose ancestral links are increasingly multi-generational and where only a small proportion of those claiming Irish ancestry in America are immigrants. The distance between second, third, fourth, and fifth generation Irish-Americans and Ireland may make them less directly connected, but certain events in their ethnic homeland may mobilize them when they feel key achievements like peace are threatened.

Cowell-Meyers and Gallaher provide multiple reinforcing reasons for the success and influence of Irish America in the aftermath of Brexit. First, they note that “Irish America has maintained a coherent political culture and an almost ‘tribal’ bond” (p. 15). The lobby relied on long-established networks of influence, especially by members of Congress and other high-level government officials, which allowed the Irish to be effective. St. Patrick’s Day celebrations provided Irish-American lobbyists direct access to Congress, policymakers in the executive branch, and Irish and Northern Irish leaders. Finally, Irish America has benefitted from becoming an admired ethnic group in America, so its influence extends beyond the diaspora to members of the general public who are sympathetic to the Irish cause.

One of the interesting findings of this research is that while Irish America proved effective in preventing a hard border after Brexit, it failed to prevent the British from passing the Legacy Bill, which ended criminal investigations into the unsolved murders during the Troubles era in Northern Ireland, including those allegedly committed by state forces. Many Irish-Americans had been motivated to believe that justice be served, especially against those members of the British defense forces or Protestant paramilitaries who had been identified as the perpetrators of crimes leading to the death of many Irish nationalists and republicans from the late 1960s through the 1990s. Cowell-Meyers and Gallaher attribute the diaspora’s failure to stop the legacy legislation to the bill’s disconnection from economic incentives and to the British Conservative Party’s firm stance on the matter. Many Tory members saw it as a domestic issue and were unwilling to be influenced by external actors who might seek to embarrass the British government over its previous collusion or direct involvement with the killing of Catholics during the Troubles. The need to prevent a hard border on the island of Ireland, by contrast, was clearly linked to trade with the European Union and aligned with American policy, which has historically sought to facilitate global commerce. It was more difficult for the Americans to directly challenge British domestic security than it was to make the case for maintaining future international trade.

Building the Green Wall thus provides a measured and nuanced view of the role of Irish America in the aftermath of Brexit. While some in the diaspora often exaggerate its importance, Cowell-Meyers and Gallaher provide a detailed and impeccably well-researched analysis. Thus, this book is an important addition to the well-established history of the Irish diaspora in the United States and provides important insight into understanding when and why ethnic lobbies gain power and influence over the making of US foreign policy.