The "very fragmented" nature of the market however, has led Barrett to the conclusion barriers to entry are "very high."
This is mainly due to every US state requiring a separate local license, provoking a more patient approach from Trustly.
But the payments provider will still be closely monitoring the situation in the US.
Barrett told Gambling Insider: "We are monitoring the regulatory situation in the US closely as it poses a great opportunity for us.
"However, the US is a very fragmented market and each state requires a local license, which makes the barriers to entry very high. Still, international expansion outside Europe is in our long-term plan and we foresee huge potential, not only in Europe, but globally."
Looking ahead to 2019, Barrett believes the biggest challenge facing Trustly is responding to regulatory demands, with Sweden providing a specific example.
"The biggest challenges in the coming year will be navigating the increasingly complex regulatory landscape," he explained.
"In Sweden, for instance, new gambling legislation enters into effect on 1 January. The new regulations will impact our operators, which means they also directly impact us.
"As a result, we may be forced to suspend our services if we have reason to believe an operator is deemed by the Swedish Gaming Authority or any Swedish court of law not to comply with the Gaming Act.
"However, we believe that Pay N Play will assist licensed operators in ensuring their compliance with the player registration and responsible gaming requirements. We have expert legal and compliance teams on board working hard to interpret new legislation, apply for relevant licenses and support our operators."
Barrett was speaking exclusively for the January/February 2019 issue of the Gambling Insider magazine. Register here for free access to the full interview when it is published.