The funds were placed under review following the departures of managers Stephen Moore and head of US equities Cormac Wheldon for Artemis Fund Managers.
Both funds now hold neutral ratings whereas the American fund held a bronze rating and the American Select fund held a silver rating.
Despite Threadneedle replacing these managers with Nadia Grant and Diane Sobin, Morningstar OBSR says: “Threadneedle has additionally made significant hires to strengthen its US equity team; however, it is still early days for the team and Morningstar OBSR feel that a Neutral rating is appropriate at this stage.”
A spokeswoman for Threadneedle Investments says: “We understand that Morningstar have to regularly review their ratings.
“However we now have our most experienced US equities team in place, boasting a total of 154 years’ experience in the industry. We are confident that under Diane Sobin’s leadership we will continue to deliver strong results for our clients.”
Elsewhere Morningstar has rated the £2.2bn Threadneedle European Select fund to bronze in its first rating.
The rating agency says: ” The manager David Dudding primarily adopts a bottom-up approach, focusing on quality companies with sustainable growth characteristics. Dudding has demonstrated his abilit to add value over the long term and Morningstar OBSR views this fund as a strong option for investors.”
Morningstar OBSR adds: “The managers work in a collegial way with the wider UK equity team at Kames to support idea generation and stock selection for the fund. However, as individuals, they have proven themselves adept at running the fund and have delivered a consistent and competitive return profile since its launch in 2010. Morningstar OBSR therefore believes the fund is deserving of a bronze rating.”